Two different families A and B are blessed with equal number of children. There are 3 tickets to be…

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 112, then the number of children in each family is
  1. 6
  2. 5
  3. 3
  4. 4

Solution

Let n number of children be there in each family.

112= nC3·3! 2nC3·3!

⇒ nC3 2nC3=112 

⇒nn-1n-22n2n-12n-2=112

⇒n-22n-1=13

⇒3n-6=2n-1

⇒n=5

Asked in: JEE Main 2018 (16 Apr Online)

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