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How many numbers between 1 to 10^10 contain 1 in them?

+1 vote
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How many numbers between 1 to 10^10 contain 1 in them?
posted Jul 18, 2018 by anonymous

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1 Answer

+1 vote

number of 1s between 1 and 10 {excluding 1 and 10} = 0
number of 1s between 1 and 100 {excluding 1 and 100} = 19
number of 1s between 1 and 1000 {excluding 1 and 1000} = 299
number of 1s between 1 and 10000 {excluding 1 and 10000} = 3999
We can see a pattern here: The number of 1s between 1 and 10^n = n*10^(n-1) - 1.
Therefore to calculate the number 1s between 1 and 10^10 :
10*10^(10 - 1) - 1 = **********.

answer Jul 18, 2018 by Tejas Naik
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