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One day, Larry writes down the numbers 1, 2, ..., 999. Larry chooses one of the digits written down at random. What is the probability that Larry chooses a 7?

 Mar 9, 2020
 #1
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The probability that Larry chooses a 7 is 28/297.

 Mar 9, 2020
 #2
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There are a total of 2889 digits between 1 and 999. 

 

There are exactly 300 "7s" between 1 and 999, including duplicates such as: 77, 777........etc.

 

Then the probability is:300 / 2889 = ~0.10384 x 100 =10.384%.

 Mar 9, 2020

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