How many three-digit numbers are there? - Vidyadip

Question

How many three-digit numbers are there?

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Answer

We cannot have a Oat the hundred's place. So, the hundred's place can be filled with any of the 9 digits 1, 2, 3 ..... , 9. So, there are 9 ways of filling the hundred's place. Ten's place can be filled with any 10 digits in 10 ways. Now, the unit's place can be filled with any 10 digits in 10 ways. Hence, the total number of required numbers = 9 × 10 × 10 = 900

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