How many digits are needed to write down all from 1-100?

To determine how many digits are needed to write down all numbers from 1 to 100, we need to consider the following:

1. Count the digits in numbers from 1 to 9: These numbers have one digit each.
- There are a total of 9 one-digit numbers: 1, 2, 3, 4, 5, 6, 7, 8, and 9.

2. Count the digits in numbers from 10 to 99: These numbers have two digits each.
- There are a total of 90 two-digit numbers: 10, 11, 12, ..., 97, 98, and 99.

3. Count the digits of the number 100: This number has three digits.

Now, let's calculate the total number of digits:

Total number of one-digit numbers = 9 x 1 = 9 digits
Total number of two-digit numbers = 90 x 2 = 180 digits
Total number of three-digit numbers = 1 x 3 = 3 digits

Adding up these totals, we get:

9 + 180 + 3 = 192

Therefore, to write down all numbers from 1 to 100, you would need a total of 192 digits.