$25$ persons are in a room. $15$ of them play hockey, $17$ of them play football and $10$ of them play both hockey and football. Then the number of persons playing neither hockey nor football is:
D. 3 No. of persons who play either football or hockey $= 15 + 17 - 10 = 22$ No. of persons playing neither hockey nor football $= 25 - 22 = 3$
Apply Principle of mutual Inclusion $-$Exclusion
$n(A\cup B)=n(A)+n(B)-n(A\cap B)$
64.3k questions
77.9k answers
243k comments
79.7k users