UPSC Prelims 2018·CSAT·Quantitative Aptitude·Combinatorics and Probability

19 boys turn out for playing hockey. Of these, 11 are wearing hockey shirts and 14 are wearing hockey pants. There are no boys without shirts and/or pants. What is the number of boys wearing full uniform?

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Last updated 23 May 2026, 3:31 pm IST
  1. A3
  2. B5
  3. C6Correct
  4. D8

Explanation

Here's a brief explanation: 1. Total number of boys = 19. 2. Number of boys wearing hockey shirts = 11. 3. Number of boys wearing hockey pants = 14. 4. The statement "There are no boys without shirts and/or pants" means that every boy has at least a shirt or pants (or both). In set theory terms, the union of boys with shirts and boys with pants is equal to the total number of boys, which is 19. 5. We need to find the number of boys wearing full uniform, which means wearing both shirts AND pants. This is the intersection of the two groups. 6. Using the principle of inclusion-exclusion for two sets: Total = (Boys with shirts) + (Boys with pants) - (Boys with both) 19 = 11 + 14 - (Boys with both) 19 = 25 - (Boys with both) 7. Solving for "Boys with both": Boys with both = 25 - 19 = 6. Therefore, the number of boys wearing full uniform is 6. Option A (3) is incorrect. Option B (5) is incorrect. Option C (6) is correct. Option D (8) is incorrect.
Quantitative Aptitude: 19 boys turn out for playing hockey. Of these, 11 are wearing hockey shirts and 14 are wearing hockey pants. There are n

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