How many two-digit numbers are there that have the tens digit less than the ones digit?

1. A two-digit number is given with the tens digit less than the ones digit.

Let’s count the number of such numbers.

2. If there is 1 in the tens place, then in the ones place – any of the numbers from 2 to 9 – 8 options.

If the tens digit is 2, the second position is a number from 3 to 9 – 7 options.

Accordingly, if the first digit is 3 – 6 options, and so on.

When the first position is 8, the last digit is 9 – 1 option.

3. Let’s count the total number of combinations.

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = 9 * 4 = 36 numbers.

Answer: 36 such numbers