Mathematics
How many times does the digit 3 occur at ten's place in natural numbers from 100 to 1000?
Answer
We need to count natural numbers from 100 to 1000 in which the digit at the ten's place is 3.
Such numbers are of the form 3 (a 3-digit number with 3 at the ten's place), as the number 1000 has 0 at its ten's place.
For the hundred's place, the digit can be any of 1, 2, 3, 4, 5, 6, 7, 8 or 9 (9 choices).
For the ten's place, the digit is fixed as 3 (1 choice).
For the unit's place, the digit can be any of 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9 (10 choices).
Total such numbers = 9 × 1 × 10
= 90
Hence, the digit 3 occurs at the ten's place 90 times in natural numbers from 100 to 1000.
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