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Dice total divided by the better of two dice

Question

A game uses two fair dice. First you throw both and record their sum as your score. Then you throw both again and divide your score by the value of one of these two dice, choosing whichever die you like; the quotient is your final result. Playing to maximise your result, what is its expected value?

Short answer

2779/720≈3.862779/720\approx3.86. You always divide by the smaller die. The two throws are independent, so the answer is 7⋅E[1/min⁡]7\cdot E[1/\min], where P(min⁡=k)=13−2k36P(\min=k)=\tfrac{13-2k}{36}. This gives E[1/min⁡]=397720E[1/\min]=\tfrac{397}{720} and the result 2779720\tfrac{2779}{720}.

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

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