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