Two different families A and B are blessed with equal number of children. There are 3 tickets to be distributed amongst the children of these families so that no child gets more than one ticket. If th

Question

Two different families A and B are blessed with equal number of children. There are 3 tickets to be distributed amongst the children of these families so that no child gets more than one ticket. If the probability that all the tickets go to the children of the family B is 1 12 , then the number of children in each family is

TestHub · Accepted Answer

Let n number of children be there in each family. 1 12 = n C 3 · 3 ! 2 n C 3 · 3 ! ⇒ n C 3 2 n C 3 = 1 12 ⇒ n n - 1 n - 2 2 n 2 n - 1 2 n - 2 = 1 12 ⇒ n - 2 2 n - 1 = 1 3 ⇒ 3 n - 6 = 2 n - 1 ⇒ n = 5

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