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Brent rolls a fair dodecahedral die with numbers 1,2,3,...,11,12 on its faces. What is the expected number of digits in the number he obtains? Express your answer in a decimal.

 Apr 2, 2021
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The probability that he gets 1 digit is 9/12=3/4, and the probability that he gets 2 digits is 3/12 = 1/4, so the expected number of digit he obtains is:

3/4*1+1/4*2=1.25

 Apr 2, 2021

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