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NDA 2020 Maths · Mathematics · Sets, Relations and Functions · easy

In a class, 20 students play cricket, 15 play hockey and 6 play both. How many students play exactly one of the two games?

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In a class, 20 students play cricket, 15 play hockey and 6 play both. How many students play exactly one of the two games?
  1. A. 29
  2. B. 21
  3. C. 35
  4. D. 23
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Answer: (D) 23

Only cricket =20−6=14=20-6=14 and only hockey =15−6=9=15-6=9, so exactly one game =14+9=23=14+9=23. The value 29 is n(A∪B)n(A\cup B), which includes the 6 who play both, and 35 is just 20+1520+15 with the overlap counted twice.
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Original question written in the NDA 2020 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake