Two friends `Aa n dB` have equal number of daughters. There are three cinema tickets which are to be distributed among the daughters of `Aa n dB` . The probability that all the tickets go to the daughters of `A` is 1/20. Find the number of daughters each of them have.

Answer

3

Explanation

Let each of the two friends have n daughters. Then probability that all the tickets go to the daughters of A is
`(.^(n)C_(3))/(.^(2n)C_(3)) = (n - 2)/(4(2n - 1)) = (1)/(20)`
`implies n = 3`