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How many numbers are there between 99 and 1000 having 7 in the units place?

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Question

How many numbers are there between 99 and 1000 having 7 in the units place?

Sum
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Solution

First note that all these numbers have three digits.

7 is in the unit’s place.

The middle digit can be any one of the 10 digits from 0 to 9.

The digit in hundred’s place can be any one of the 9 digits from 1 to 9.

Therefore, by the fundamental principle of counting

There are 10 × 9 = 90 numbers between 99 and 1000 having 7 in the unit’s place.

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Chapter 7: Permutations and Combinations - Solved Examples [Page 116]

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NCERT Exemplar Mathematics [English] Class 11
Chapter 7 Permutations and Combinations
Solved Examples | Q 2.(i) | Page 116

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