How many four-digit positive integers are there that contain the digit 1?
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Originally Posted by alexmahone How many four-digit positive integers are there that contain the digit 1? To be clear is not a four digit number, right??
There are four-digit numbers.
Of those there are that do not contain any 1's.
So how many contain at least one 1?
should the digits be the same or must be different?
if they are the same then there are:
if they are not the same then there are:
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