Homework Answers
The possible positive integers between 1 and 10n is 10n.
The digit 7 can be at any position from 1 to n in those numbers. Apart from digit 7, there are 9 possible digits.
All possible positive integers between 1 and 9999....n times and not containing 7 is 9 * 9 * ... n times = 9n - 1 (We subtracted by -1 as 0 is also one of possible number which do not contain 7 and we do not want to count the value 0)
The number 10n does not contain the digit 7.
So, possible positive integers between 1 and 10n and not containing 7 is 9n -1 + 1 = 9n
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Exercise 6: How many positive integers between 1 and 10", with n 1 a positive integer,...
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