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प्रश्न
How many three-digit numbers are there with 3 in the unit place?
with repetition
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उत्तर
With repetition
The unit place is filled (by 3) in 1 way
The 10’s place can be filled in 10 ways
The 100’s place can be filled in 9 ways (excluding 0)
So the number of 3 digit numbers with 3 unit – place = 9 × 10 × 1 = 90
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