Question 58

Out of 20 consecutive positive integers, two are chosen at random. The probability that their sum is odd is

Solution

You have to choose Odd-Even or Even-Odd.

The probabilities of both events are the same: at the start there’s the same amount of odds and evens.

So calculate for one of them and multiply by $2$ .

First number being odd: $10/ 20 =$

Second number being even: $10/ 19$

Overall = 10/19*2 *2 = 10/19

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