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SSC Quantitative Aptitude Number System and its Operations Question Bank Set Theory (II)

  • question_answer
    Of the members of three athletic teams in a school, 21 are in the cricket team, 26 are in the hockey team and 29 are in the football team. Among them, 14 play hockey and cricket, 15 play hockey and football, 12 play football and cricket. 8 play all the three games. The total number of members in the three athletic teams is

    A) 43

    B) 76

    C) 49

    D) None of these

    Correct Answer: A

    Solution :

    [a] Let C, H, F denote the sets of members who are on the cricket team, hockey team and football team, respectively. Then, we are given \[n\,(C)=21,\]\[n\,(H)=26,\]\[n\,(F)=29\] \[n\,(H\cap C)=14,\]\[n\,(H\cap F)=15,\] \[n\,(F\cap B)=12\] and\[n\,(C\cap H\cap F)=8\] We have to find \[n\,(C\cup H\cup F).\] To find this, we use the formula \[n\,(C\cup H\cup F)=n\,(C)+n\,(H)+n\,(F)\] \[-\,n\,(C\cap H)-n\,(H\cap F)\] \[-n\,(F\cap C)+n\,(C\cap H\cap F)\] Hence, \[n\,(C\cup H\cup F)=(21+26+29)\] \[-\,(14+15+12)+8=43\] Thus, there are 43 members in all.


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