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