Question

If out of 20 consecutive whole numbers two are chosen at random, then find the probability that their sum is odd.

Answer 1

Correct Answer - `(10)/(19)`
The total number of ways in which 2 integers can be chosen from the given 20 integers is `.^(20)C_(2)`.
The sum of the selected numbers is odd if exactly one of them is even and only one is odd. Therefore, the favorable number of outcomes is `(.^(10)C_(1)xx.^(10)C_(1))/(.^(20)C_(2)) = (10)/(19)`