One day, River writes down the numbers \(1, 2, \dots, 999.\) River chooses one of the digits written down at random. What is the probability that River chooses a 7?
Please fix the LaTeX.
189 , 300 , 300 , 300 , 300 , 300 , 300 , 300 , 300 , 300 >>Total = 2889
As you can see, there 300 7 between 1 and 999, counting duplicates such as 177, 777.....etc. The total of all digits from 1 to 999 =2,889.
Therefore, the probability is =300 / 2889 =100 / 963
This is from the AoPs intro to counting and probability class...
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