Set Counting — Sports Participation in a Class Three-fourths of the boys play football, one-half play cricket, and one-fourth of the cricket players do not play football. What fraction of boys play neither cricket nor football?

Difficulty: Medium

Correct Answer: One-eighth of the boys play neither cricket nor football.

Explanation:


Introduction / Context:
This is a classic two-set (football and cricket) counting problem. We are given overall fractions for football and cricket participation and an additional constraint about a portion of cricket players not playing football. We must find the fraction who play neither game.



Given Data / Assumptions:

  • Total boys = 1 (use unit method for fractions).
  • Football (F) = 3/4 of boys.
  • Cricket (C) = 1/2 of boys.
  • Among cricket players, 1/4 do not play football ⇒ C-only = (1/4) * (1/2) = 1/8.


Concept / Approach:
Use set identities: total = F-only + C-only + both + neither. Also, F = F-only + both, and C = C-only + both. Solve systematically.



Step-by-Step Solution:

Let total boys T = 1.Given C = 1/2. C-only = 1/8. Therefore, both = C − C-only = 1/2 − 1/8 = 3/8.Given F = 3/4. Since both = 3/8, F-only = F − both = 3/4 − 3/8 = 3/8.Sum known participants = F-only + C-only + both = 3/8 + 1/8 + 3/8 = 7/8.Neither = 1 − 7/8 = 1/8.


Verification / Alternative check:
Check totals: 3/8 (F-only) + 3/8 (both) = 3/4 = F, OK. 1/8 (C-only) + 3/8 (both) = 1/2 = C, OK. Complement gives 1/8 neither, consistent.



Why Other Options Are Wrong:

  • Two-third only football / Two-fifth only football: incompatible with F = 3/4 and computed overlap.
  • One-fourth or One-third neither: contradict the computed 1/8 neither.


Common Pitfalls:
Forgetting that “one-fourth of cricket players do not play football” applies to cricket subset only, or double-counting the intersection.



Final Answer:
One-eighth of the boys play neither cricket nor football.

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