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The questions your board exam loves to ask

800 most-asked Class 11 & 12 (+1 / +2) questions across Physics, Chemistry, Maths and Biology — each with a model answer and the exact marking-scheme points examiners reward. Revise smart, walk in calm.

800 board questions•Model answers•Marking-scheme points•Every chapter•CBSE · ISC · State boards

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MathsClass 112 markseasy

Sets

If A = {1, 2, 3}, write the power set of A and state n(P(A)).

Reveal model answer + marking points▾

The power set is the set of all subsets of A. P(A) = { {}, {1}, {2}, {3}, {1,2}, {1,3}, {2,3}, {1,2,3} }. The number of elements n(P(A)) = 2^n = 2^3 = 8.

n(P(A)) = 2^n

Marking-scheme points

  • ✓Power set = set of all subsets (including empty set and A itself)
  • ✓List all 8 subsets
  • ✓n(P(A)) = 2^3 = 8

The concept

The power set is the set of ALL subsets of a set, including the empty set and the set itself.

Why it matters

Power sets underpin logic, probability and computer science (every combination of options).

💡 Memory trick

n elements -> 2^n subsets. For {1,2,3}: 2^3 = 8 subsets.

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MathsClass 112 markseasy

Sets

In a class of 35 students, 24 like cricket and 16 like football. If each student likes at least one of the two games, how many like both?

Reveal model answer + marking points▾

Let n(C) = 24, n(F) = 16, n(C union F) = 35 (each likes at least one). By the formula n(C union F) = n(C) + n(F) - n(C intersection F), we get 35 = 24 + 16 - n(C intersection F), so n(C intersection F) = 40 - 35 = 5. Hence 5 students like both games.

n(A union B) = n(A) + n(B) - n(A intersection B)

Marking-scheme points

  • ✓n(C union F) = n(C) + n(F) - n(C intersection F)
  • ✓35 = 24 + 16 - x
  • ✓x = 5 students like both
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MathsClass 112 markseasy

Sets

Define union, intersection and difference of two sets with an example each.

Reveal model answer + marking points▾

Union (A union B) is the set of all elements that are in A or in B or in both. Intersection (A intersection B) is the set of elements common to both A and B. Difference (A - B) is the set of elements that are in A but not in B. Example: if A = {1,2,3} and B = {2,3,4}, then A union B = {1,2,3,4}, A intersection B = {2,3}, and A - B = {1}.

Marking-scheme points

  • ✓Union: elements in A or B (or both)
  • ✓Intersection: elements common to A and B
  • ✓Difference A - B: in A but not in B
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