For Class 8, 9 & 10

Master the basics - and everything after gets easier

Concept-first questions with clear model answers in Physics, Chemistry, Maths and Biology, all NCERT-aligned. Start early, build the habit, and walk into your boards, NEET and JEE already ahead.

Interactive lessons

learn by playing

Drag, slide and build - watch each concept come alive, then reveal the answer.

200 interactive lessons

Interactive

Ohm's law

Class 10 Physics

Slide V & R, watch the bulb glow

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Interactive

pH scale

Class 10 Chemistry

Slide across acids and bases

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Interactive

Atomic number and mass number

Class 9 Chemistry

Add protons & neutrons, build shells

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Interactive

Laws of reflection

Class 8 Physics

Change the angle, watch it bounce

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Interactive

Volume of a sphere

Class 9 Maths

Grow the radius, see the volume

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Interactive

Area of a trapezium

Class 8 Maths

Drag the sides, read the area

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Interactive

Power of a lens

Class 10 Physics

Move the object, trace the rays

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Interactive

Food chain and energy flow

Class 10 Biology

Follow the energy as it flows

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Interactive

Speed

Class 8 Physics

Slide distance & time, watch the speed

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Interactive

Density

Class 9 Physics

Pack mass into volume, float or sink

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Interactive

Work done

Class 9 Physics

Push harder or farther, watch work grow

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Interactive

Kinetic energy

Class 9 Physics

Speed it up - energy grows with the square

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Interactive

Power of a lens

Class 10 Physics

Shorten the focal length, boost the power

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Interactive

Mole concept

Class 9 Chemistry

Weigh out grams, count the moles

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Interactive

Avogadro's number

Class 9 Chemistry

Add moles, count the particles

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Interactive

Microscope magnification

Class 8 Biology

Grow the image, read the magnification

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Interactive

Population density

Class 10 Biology

Add individuals, shrink the land, see crowding

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Interactive

Simple interest

Class 8 Maths

Slide money, rate & time, watch interest

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Interactive

Pythagoras theorem

Class 9 Maths

Stretch the two sides, get the hypotenuse

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Interactive

Probability of an event

Class 10 Maths

Change the outcomes, watch the odds

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Interactive

Newton's second law

Class 9 Physics

Push a mass, pick an acceleration

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Interactive

Momentum

Class 9 Physics

Slide mass & velocity, build momentum

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Interactive

Pressure

Class 8 Physics

Shrink the area, feel the pressure rise

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Interactive

Weight

Class 9 Physics

Change the planet's gravity, watch your weight

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Interactive

Refractive index

Class 10 Physics

Slow light in the medium, raise the index

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Interactive

Resistors in series

Class 10 Physics

Add two resistors in a line

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Interactive

Mass percentage of a solution

Class 9 Chemistry

Dissolve solute, read the strength

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Interactive

Concentration of a solution

Class 9 Chemistry

Pack solute into less liquid

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Interactive

Population change

Class 10 Biology

Balance births against deaths

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Interactive

Compound microscope

Class 8 Biology

Combine eyepiece & objective lenses

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Interactive

Area of a circle

Class 8 Maths

Grow the radius, watch the area square

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Interactive

Volume of a cuboid

Class 8 Maths

Stretch length, breadth & height

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Interactive

Electronic configuration and valency

Class 9 Chemistry

Slide the atomic number, build the atom

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Interactive

Homologous series (alkanes)

Class 10 Chemistry

Add carbons, name the compound

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Interactive

Mass number

Class 9 Chemistry

Add protons & neutrons, get the mass number

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Interactive

Power

Class 9 Physics

More work in less time = more power

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Interactive

Potential energy

Class 9 Physics

Lift a mass higher, store energy

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Interactive

Wave speed

Class 9 Physics

Tune frequency & wavelength, set the speed

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Interactive

Electric current

Class 10 Physics

Push charge per second, get the current

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Interactive

Percentage

Class 8 Maths

Compare part to whole as a %

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Interactive

Electron dot structure

Class 9 Chemistry

Draw valence electrons as dots

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Interactive

Acceleration

Class 9 Physics

Speed up over time, find acceleration

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Interactive

Distance, speed and time

Class 8 Physics

Set speed & time, cover the distance

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Interactive

Frequency and time period

Class 9 Physics

Shorten the period, raise the frequency

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Interactive

Heating effect of current

Class 10 Physics

Raise the current, watch heating soar

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Interactive

Area of a triangle

Class 8 Maths

Set base & height, halve the rectangle

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Interactive

Area of a rectangle

Class 8 Maths

Set length & breadth, fill the area

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Interactive

Mean (average)

Class 9 Maths

Share the total equally across items

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Interactive

Discount

Class 8 Maths

Slide price & % off, see the saving

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Interactive

Heart rate

Class 10 Biology

Set heart rate & time, count the beats

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Interactive

Resistors in parallel

Class 10 Physics

Wire two resistors side by side

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Interactive

Electric charge

Class 10 Physics

Flow current over time, collect charge

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Interactive

Electrical energy and units

Class 10 Physics

Run appliances, add up the units

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Interactive

Kelvin temperature scale

Class 9 Chemistry

Slide Celsius, read the Kelvin

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Interactive

Moles from number of particles

Class 9 Chemistry

Divide particles by Avogadro's number

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Interactive

Ten percent law

Class 10 Biology

See 10% of energy reach the next level

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Interactive

Area of a square

Class 8 Maths

Grow the side, square the area

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Interactive

Volume of a cube

Class 8 Maths

Grow the edge, cube the volume

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Interactive

Circumference of a circle

Class 8 Maths

Grow the radius, roll out the rim

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Interactive

Surface area of a cube

Class 9 Maths

Grow the edge, cover six faces

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Interactive

Potential difference

Class 10 Physics

Share work across charge, get volts

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Interactive

Resistance from Ohm's law

Class 10 Physics

Divide voltage by current, get resistance

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Interactive

Echo and SONAR

Class 9 Physics

Time the echo, find the distance

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Interactive

Mass from moles

Class 9 Chemistry

Multiply moles by molar mass

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Interactive

Breathing rate

Class 10 Biology

Set breathing rate & time

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Interactive

Volume of a cylinder

Class 10 Maths

Set radius & height, fill the can

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Interactive

Compound interest

Class 8 Maths

Compound money over years

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Interactive

Profit and loss percentage

Class 8 Maths

Set cost & selling price, see profit %

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Interactive

Perimeter of a rectangle

Class 8 Maths

Set length & breadth, walk the border

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Interactive

Surface area of a sphere

Class 10 Maths

Grow the radius, wrap the ball

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Interactive

Time period

Class 9 Physics

Raise the frequency, shrink the period

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Interactive

Relative velocity

Class 9 Physics

Two objects approach - add their speeds

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Interactive

Average velocity

Class 9 Physics

Average the start and end speeds

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Interactive

Equations of motion (v = u + at)

Class 9 Physics

Accelerate from u for a time t

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Interactive

Kelvin to Celsius

Class 9 Chemistry

Slide Kelvin, read the Celsius

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Interactive

Population growth rate

Class 10 Biology

Balance births vs deaths per population

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Interactive

Perimeter of a square

Class 8 Maths

Grow the side, walk four edges

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Interactive

Perimeter of a triangle

Class 8 Maths

Add the three sides

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Interactive

Area of a parallelogram

Class 8 Maths

Set base & height, slide the shape

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Interactive

Area of a rhombus

Class 8 Maths

Set the two diagonals

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Interactive

Equations of motion (distance)

Class 9 Physics

Start, accelerate, cover ground

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Interactive

Joule's law of heating

Class 10 Physics

Raise current, resistance or time

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Interactive

Electric power (P = VI)

Class 10 Physics

Multiply voltage by current

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Interactive

Average atomic mass of isotopes

Class 9 Chemistry

Mix two isotopes by abundance

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Interactive

Seed germination percentage

Class 9 Biology

Count sprouted seeds out of the total

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Interactive

Volume of a cone

Class 9 Maths

Set radius & height, fill the cone

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Interactive

Surface area of a cylinder

Class 9 Maths

Wrap the side and both ends

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Interactive

Surface area of a cuboid

Class 9 Maths

Cover all six rectangular faces

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Interactive

nth term of an AP

Class 10 Maths

Step from the first term by d

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Interactive

Sum of an AP

Class 10 Maths

Add up the first n terms

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Interactive

Focal length of a mirror

Class 10 Physics

Halve the radius to find the focus

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Interactive

Speed of light in a medium

Class 10 Physics

Raise the index, slow the light

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Interactive

Percentage purity

Class 9 Chemistry

Weigh the pure part of a sample

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Interactive

Slope of a line

Class 10 Maths

Rise over run gives the steepness

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Interactive

Percentage change

Class 8 Maths

Compare a new value to the old

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Interactive

Volume of a hemisphere

Class 9 Maths

Grow the radius of half a ball

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Interactive

Area of a sector

Class 10 Maths

Cut a slice of angle from a circle

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Interactive

Length of an arc

Class 10 Maths

Measure the curved edge of a slice

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Interactive

Slant height of a cone

Class 9 Maths

Combine radius & height for the slant

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Interactive

Unit conversion (km/h to m/s)

Class 9 Physics

Convert km/h into m/s

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Interactive

Equations of motion (v^2 = u^2 + 2as)

Class 9 Physics

Accelerate over a distance, find v

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Interactive

Impulse

Class 9 Physics

Hit harder or longer, change momentum

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Interactive

Wavelength

Class 9 Physics

Speed over frequency gives wavelength

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Interactive

Oscillations

Class 9 Physics

Vibrate at a frequency for a time

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Interactive

Cost of electricity

Class 10 Physics

Units times rate gives the bill

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Interactive

Number of neutrons

Class 9 Chemistry

Take protons away from the mass number

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Interactive

Curved surface area of a cone

Class 9 Maths

Wrap the slanted side of a cone

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Interactive

Total surface area of a cone

Class 9 Maths

Add the base circle to the cone's side

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Interactive

Curved surface area of a hemisphere

Class 9 Maths

Cover the dome of a hemisphere

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Interactive

Diagonal of a square

Class 9 Maths

Cross a square corner to corner

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Interactive

Unit conversion (m/s to km/h)

Class 9 Physics

Convert m/s into km/h

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Interactive

Distance from velocities

Class 9 Physics

From two speeds, find the distance

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Interactive

Diagonal of a rectangle

Class 9 Maths

Cross a rectangle corner to corner

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Interactive

Diagonal of a cuboid

Class 9 Maths

The longest rod that fits in a box

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Interactive

Area by Heron's formula

Class 9 Maths

Area from just the three sides

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Interior angle sum of a polygon

Class 8 Maths

Add up a polygon's inside angles

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Exterior angle of a regular polygon

Class 8 Maths

Share 360 among a polygon's corners

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Number of diagonals of a polygon

Class 8 Maths

Count the diagonals of a polygon

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Interactive

Discriminant

Class 10 Maths

Test how many roots a quadratic has

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Interactive

Sum of roots

Class 10 Maths

Sum of a quadratic's roots

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Interactive

Punnett square (monohybrid cross)

Class 10 Biology

Cross two parents, predict the offspring

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Interactive

Balancing chemical equations

Class 10 Chemistry

Slide coefficients until atoms balance

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Interactive

Writing chemical formulae (valency)

Class 9 Chemistry

Criss-cross valencies into a formula

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Interactive

Current from power

Class 10 Physics

Divide power by voltage for current

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Interactive

Power (P = V^2 / R)

Class 10 Physics

Voltage squared over resistance

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Interactive

Sine ratio

Class 10 Maths

Opposite over hypotenuse

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Interactive

Cosine ratio

Class 10 Maths

Adjacent over hypotenuse

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Interactive

Tangent ratio

Class 10 Maths

Opposite over adjacent

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Interactive

Area of an equilateral triangle

Class 9 Maths

Area of an equilateral triangle

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Interactive

Curved surface area of a cylinder

Class 9 Maths

Wrap only the curved side

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Interactive

Loss percentage

Class 8 Maths

Sell below cost, find the loss %

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Interactive

Amount with simple interest

Class 8 Maths

Principal plus its simple interest

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Interactive

Distance formula

Class 10 Maths

Straight distance between two points

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Interactive

States of matter

Class 9 Chemistry

Heat particles solid → liquid → gas

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Interactive

Parts of a plant cell

Class 8 Biology

Tap a cell part to see its job

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Interactive

Diagonal of a cube

Class 9 Maths

Longest diagonal through a cube

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Total surface area of a hemisphere

Class 9 Maths

Dome plus its flat circle

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Interactive

Sum of first n natural numbers

Class 10 Maths

Add 1 + 2 + ... + n instantly

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Interactive

Range of data

Class 9 Maths

Spread from smallest to largest

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Interactive

Class mark

Class 9 Maths

Midpoint of a class interval

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Interactive

Selling price from profit percent

Class 8 Maths

Mark up cost by a profit %

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Interactive

Perimeter of a sector

Class 10 Maths

Two radii plus the curved arc

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Circumference from diameter

Class 8 Maths

Circumference straight from diameter

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Interactive

Power (P = F x v)

Class 9 Physics

Force times velocity gives power

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Interactive

Percentage of a number

Class 8 Maths

Find a percentage of a number

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Interactive

Series and parallel circuits

Class 10 Physics

Break a bulb in series vs parallel

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Interactive

Symbols of elements

Class 9 Chemistry

Match each element to its symbol

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Interactive

Free fall (velocity)

Class 9 Physics

Drop from a height, hit this speed

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Free fall (time)

Class 9 Physics

How long a drop takes

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Free fall (distance)

Class 9 Physics

Distance fallen in a given time

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Complement of an event

Class 10 Maths

Chance an event does NOT happen

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Product of roots

Class 10 Maths

Product of a quadratic's roots

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Exterior angle theorem

Class 9 Maths

Exterior angle = sum of remote interiors

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Complementary angles

Class 10 Maths

What adds to 90 degrees

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Supplementary angles

Class 9 Maths

What adds to 180 degrees

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Perimeter of a semicircle

Class 10 Maths

Curved half plus the diameter

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Area of a semicircle

Class 10 Maths

Half the area of a circle

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Turning effect (moments)

Class 9 Physics

Balance the see-saw with moments

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Interactive

Reflex arc

Class 10 Biology

Step through a reflex, stimulus to action

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Interactive

Buoyant force (upthrust)

Class 9 Physics

Displace liquid, feel the upthrust

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Interactive

Relative density

Class 9 Physics

Compare a density to water's

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Interactive

Power in lifting a load

Class 9 Physics

Lift a load, faster needs more power

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Cosecant ratio

Class 10 Maths

Hypotenuse over opposite

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Secant ratio

Class 10 Maths

Hypotenuse over adjacent

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Cotangent ratio

Class 10 Maths

Adjacent over opposite

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Interactive

Height from angle of elevation

Class 10 Maths

Height from an angle of elevation

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Interactive

Area of a quadrant

Class 10 Maths

A quarter of a circle's area

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Interactive

Interior angle of a regular polygon

Class 8 Maths

One inside angle of a regular polygon

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Interactive

Sum of first n odd numbers

Class 10 Maths

Add the first n odd numbers

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Sum of first n even numbers

Class 10 Maths

Add the first n even numbers

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Interactive

Quadratic formula (a root)

Class 10 Maths

Larger root of a quadratic

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Interactive

LCM from HCF

Class 10 Maths

LCM from the product and HCF

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Interactive

Depreciation

Class 8 Maths

Value drops by a % each year

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Interactive

Cost price from selling price

Class 8 Maths

Work back to the cost price

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Interactive

Downstream speed

Class 8 Maths

Row with the current

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Upstream speed

Class 8 Maths

Row against the current

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Interactive

Average speed for a round trip

Class 8 Maths

Average speed there and back

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Interactive

Sales tax / GST

Class 8 Maths

Tax added on a price

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Interactive

Area of a ring (annulus)

Class 10 Maths

Area of a ring between two circles

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Interactive

Edge of a cube from volume

Class 9 Maths

Edge back from the volume

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Interactive

Radius from area

Class 10 Maths

Radius back from a circle's area

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Side from area of a square

Class 8 Maths

Side back from a square's area

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Interactive

Height of a triangle from area

Class 9 Maths

Height back from area and base

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Interactive

Rate from simple interest

Class 8 Maths

Rate back from the interest

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Interactive

Time from simple interest

Class 8 Maths

Time back from the interest

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Principal from simple interest

Class 8 Maths

Principal back from the interest

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Interactive

Mean proportional

Class 10 Maths

Geometric mean of two numbers

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Interactive

Fourth proportional

Class 8 Maths

Complete the proportion a : b = c : ?

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Interactive

Marked price from selling price

Class 8 Maths

Marked price back from the sale price

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Interactive

Chambers of the human heart

Class 10 Biology

Tap a heart chamber to see its job

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Interactive

Equation of a line (y = mx + c)

Class 9 Maths

Read y off a straight line

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Interactive

Average term of an AP

Class 10 Maths

Average of first and last term

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Interactive

Number of terms in an AP

Class 10 Maths

How many terms in an AP

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Interactive

Midpoint of two points

Class 10 Maths

x-coordinate of a midpoint

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Interactive

Empirical mode

Class 10 Maths

Estimate the mode from mean & median

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Interactive

Length of a shadow

Class 10 Maths

Shadow from height and sun angle

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Interactive

Train crossing a pole

Class 8 Maths

Speed to cross a pole

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Interactive

Time and work

Class 8 Maths

More workers, fewer days

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Interactive

Dividing in a ratio

Class 8 Maths

Split a total in a ratio

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Unitary method

Class 8 Maths

Cost of a single item

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Showing 18 questions for Class 9. Tap a card to reveal the answer.

MathematicsSurface Areas and Volumesmedium

Find the volume of a sphere of radius 7 cm. (Take pi = 22/7.)

Reveal answer ↓

What it is

A sphere's volume grows with the cube of its radius: V = (4/3) pi r^3.

Interactive sphere volumer

V = 4/3 π r³ ≈ 1437.3 cm³

Sphere — slide the radius; volume grows with r³ (π = 22/7)

Answer

Volume of a sphere = (4/3) x pi x r^3 = (4/3) x (22/7) x 7^3 = (4/3) x (22/7) x 343 = (4 x 22 x 49)/3 = 4312/3, which is about 1437.3 cubic cm.

V(sphere) = (4/3) pi r^3

  • •V = (4/3) pi r^3
  • •= (4/3)(22/7)(343)
  • •= 4312/3 = about 1437.3 cm^3

Why learn this

It measures balls, planets, bubbles and tanks - anywhere something is round.

💡 Memory trick

Four-thirds pi r-cubed: V = (4/3) pi r^3 - the roundest formula in maths.

MathematicsSurface Areas and Volumeseasy

Find the surface area of a cube of side 4 units. Slide the side to explore.

Reveal answer ↓

What it is

The surface area of a cube is six times the area of one square face.

Cube surface area = 6 × side²
Surface area96 units²

Answer

Surface area = 6 x side^2 = 6 x 4^2 = 6 x 16 = 96 square units. A cube has six identical square faces, so we find the area of one face and multiply by six.

S = 6 x side^2

  • •Surface area = 6 x side^2
  • •A cube has 6 equal faces
  • •Unit: square units

Why learn this

It tells how much material wraps or paints a cubic box.

💡 Memory trick

Surface area = 6 x side^2 - six equal faces.

MathematicsSurface Areas and Volumesmedium

Find the volume of a cone of radius 3 and height 7 units (pi = 3.14159). Slide to explore.

Reveal answer ↓

What it is

The volume of a cone is one third of pi times the square of the radius times the height.

Cone volume = ⅓ × π × r² × h
Volume66.0 units³

Answer

Volume = 1/3 x pi x r^2 x h = 1/3 x 3.14159 x 3^2 x 7 = 1/3 x 3.14159 x 9 x 7 = 65.97 cubic units. A cone holds exactly one third of the cylinder with the same base and height.

V = (1/3) x pi x r^2 x h

  • •Volume = 1/3 x pi x r^2 x h
  • •One third of the matching cylinder
  • •Unit: cubic units

Why learn this

It measures the space in cones, funnels and ice-cream cones.

💡 Memory trick

Volume = 1/3 x pi x r^2 x h - a third of the cylinder.

MathematicsSurface Areas and Volumesmedium

Find the total surface area of a cylinder of radius 3 and height 7 units (pi = 3.14159). Slide to explore.

Reveal answer ↓

What it is

The total surface area of a cylinder is the curved side plus its two circular ends.

Cylinder surface = 2πr(r + h)
Total surface area188.5 units²

Answer

Total surface area = 2 pi r (r + h) = 2 x 3.14159 x 3 x (3 + 7) = 2 x 3.14159 x 3 x 10 = 188.5 square units. This is the curved surface 2 pi r h plus the two circular ends 2 pi r^2.

S = 2 pi r (r + h)

  • •Total surface = 2 pi r (r + h)
  • •Curved side (2 pi r h) + two ends (2 pi r^2)
  • •Unit: square units

Why learn this

It's the metal needed to make a closed tin or tank.

💡 Memory trick

Total surface = 2 pi r (r + h).

MathematicsSurface Areas and Volumesmedium

Find the surface area of a cuboid 3 x 4 x 5 units. Slide the dimensions to explore.

Reveal answer ↓

What it is

The surface area of a cuboid is twice the sum of the areas of its three different faces.

Cuboid surface = 2(lb + bh + hl)
Surface area94 units²

Answer

Surface area = 2(lb + bh + hl) = 2(3x4 + 4x5 + 5x3) = 2(12 + 20 + 15) = 2 x 47 = 94 square units. A cuboid has three pairs of identical faces, so we add the three distinct faces and double the total.

S = 2(lb + bh + hl)

  • •Surface = 2(lb + bh + hl)
  • •Three pairs of identical faces
  • •Unit: square units

Why learn this

It's the card needed to make a closed rectangular box.

💡 Memory trick

Surface = 2(lb + bh + hl).

MathematicsSurface Areas and Volumesmedium

Find the volume of a hemisphere of radius 6 units (pi = 3.14159). Slide to explore.

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MathematicsSurface Areas and Volumesmedium

A cone has radius 3 and height 4 units. Find its slant height. Slide to explore.

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MathematicsSurface Areas and Volumesmedium

Find the curved surface area of a cone with radius 3 and slant height 5 units (pi = 3.14159). Slide to explore.

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MathematicsSurface Areas and Volumesmedium

Find the total surface area of a cone with radius 3 and slant height 5 units (pi = 3.14159). Slide to explore.

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MathematicsSurface Areas and Volumeseasy

Find the curved surface area of a hemisphere of radius 6 units (pi = 3.14159). Slide to explore.

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MathematicsSurface Areas and Volumesmedium

Find the longest diagonal of a cuboid 3 x 4 x 12 units. Slide the dimensions to explore.

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MathematicsSurface Areas and Volumeseasy

Find the curved surface area of a cylinder with radius 3 and height 7 units (pi = 3.14159). Slide to explore.

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You have opened your 5 free lessons 🎉

Unlock every one of them — plus all four Labs, the Concept Map and an unlimited AI Tutor — with Scholar.

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MathematicsSurface Areas and Volumesmedium

Find the longest diagonal of a cube of side 5 units. Slide the side to explore.

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MathematicsSurface Areas and Volumesmedium

Find the total surface area of a solid hemisphere of radius 6 units (pi = 3.14159). Slide to explore.

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MathematicsSurface Areas and Volumesmedium

A cube has a volume of 64 cubic units. Find its edge. Slide the volume to explore.

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MathematicsSurface Areas and Volumesmedium

Find the volume of a cone of radius 3 cm and height 7 cm. (Take pi = 22/7.)

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₹1,700 ₹850 a year — about ₹2 a day

MathematicsSurface Areas and Volumesmedium

Find the surface area of a sphere of radius 7 cm. (Take pi = 22/7.)

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MathematicsSurface Areas and Volumesmedium

Find the total surface area of a closed cylinder of radius 7 cm and height 10 cm. (Take pi = 22/7.)

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₹1,700 ₹850 a year — about ₹2 a day

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