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Two coins decide how many dice: odd total

Question

Abdelrahman tosses two fair coins and then throws one fair six-sided die for every head that appeared. If no dice are thrown the total is 00. What is the probability that the total shown on the dice is odd?

Short answer

3/83/8. Condition on the number of heads: with 00 heads (prob 14\tfrac14) the total is 00, even; with 11 head (prob 12\tfrac12) one die is odd half the time; with 22 heads (prob 14\tfrac14) the sum of two dice is odd half the time. So 12⋅12+14⋅12=38\tfrac12\cdot\tfrac12+\tfrac14\cdot\tfrac12=\tfrac38.

Adapted from QuantQuestions.io; question and answer rewritten by SelfMadeQuant.com.

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