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Probability
Level
3
If a and b are relatively prime positive integers and a/b is the probability that out of a standard deck of cards you pull a K,spade, and 9 in any order with replacement, find a+b.
The answer is 341.
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1 solution
The probability of pulling a K, spade, and 9 in that order is 1/676. We must find the sum of the probabilities for each possible order to get the answer. As we have replacement, the probability is just 3!/676 = 6/676=3/338.3+338 =341.