Sure, let's break it down step by step: ### Counting 9s in the Units Place We'll count how many numbers have 9 as the last digit from 1 to 100: - 9, 19, 29, 39, 49, 59, 69, 79, 89, 99 There are 10 numbers where the units digit is 9. ### Counting 9s in the Tens Place Now, we'll count how many numbers have 9 as the tens digit from 1 to 100: - 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 There are 10 numbers where the tens digit is 9. ### Total Count Since we have 10 occurrences of 9 in the units place and 10 occurrences in the tens place, and there is no overlap between these occurrences, we simply add them together: \[ 10 \text{ (units place)} + 10 \text{ (tens place)} = 20 \] So, the digit 9 appears 20 times in the numbers from 1 to 100.
