SOLUTION: Two game tiles, numbered 1 through 9, are selected at random from a box without replacement. If their sum is even, what is the probability that both numbers are odd?
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Question 1172383: Two game tiles, numbered 1 through 9, are selected at random from a box without replacement. If their sum is even, what is the probability that both numbers are odd? Answer by ikleyn(52787) (Show Source):
If their sum is even, it means that EITHER both numbers are odd OR both numbers are even.
Among the numbers 1 to 9 inclusive, there are 5 odd and 4 even numbers.
So, P(the sum is even) = P(both are odd) + P(both are even) = = = .
From the other hand side, P(both are odd) = = .
Therefore, the conditional probability that both numbers are odd, given that their sum is even, is equal to
P(final) = = = = . ANSWER
