Total balls = 5 + 4 + 4 = 13∴ n(S) = 13C3 = 2862 blue balls can be selected from 4 balls in 4C2 = 6 ways and the remaining one ball is to be selected from 9 balls in 9C1 = 9 ways ∴ n(E) = 6 x 9∴ P(E) = 6 x 9/286 = 27/143
The least number to be added to the numbers to make them divisible by 9 is equal to the difference of the least multiple of 9 greater than the sum of the digits and sum of the digits.Sum of digits = 15.Nearest multiple of 9 greater than sum of digits = 18.Hence 3 has to be added.
Let the present age of the father be 'x' and that of the son be 'y'. Then x/y = 8/3∴ 3x = 8y Further, x + 12/y + 12 = 2/1 ∴ x + 12 = 2y + 24 ∴ x - 2y = 12 ......(ii)From eqn (i) and (ii), x = 48, y = 18 ∴ sum = 66 yrs.
EXAMIANS