How many 1 are there between 100 and 999?

To find how many times the digit '1' appears between 100 and 999, we can analyze each digit position (hundreds, tens, and units).

1. Hundreds place: The digit '1' appears in the hundreds place for the numbers 100 to 199, which contributes 100 occurrences.
2. Tens place: The digit '1' appears in the tens place for the sequences 110-119, 210-219, ..., 910-919, giving us 10 occurrences per hundred for 9 hundreds (100-900), resulting in 90 occurrences.
3. Units place: The digit '1' appears in the units place for sequences like 101, 111, ..., 191, 201, 211, ..., 901, giving 10 occurrences per hundred, totaling another 90 occurrences.

Adding these together: 100 (hundreds) + 90 (tens) + 90 (units) = 280. Thus, the digit '1' appears 280 times between 100 and 999.