2008 AMC 10B Problem 16
Problem 16 of 25IntermediateNumber TheoryCounting & Probability
Two fair coins are to be tossed once. For each head that results, one fair die is to be rolled. What is the probability that the sum of the die rolls is odd? (Note that if no die is rolled, the sum is )
Answer choices
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Solution
Whenever at least one die is rolled, by symmetry the sum is odd with probability
No die is rolled only when both coins are tails, with probability that sum is even. So the answer is
Thus, the correct answer is A.