How many 2-digit numbers are there in which the sum of its tens digit and its ones digit is equal to 8?

Answer 1

To count the number of 2-digit numbers with digits summing to 8, we can consider pairs of digits that sum to 8: $\{1,7\}$, $\{2,6\}$, $\{3,5\}$, and $\{4,4\}$. For the first three pairs, we have two ways to arrange the digits, but for the last pair, there's only one way since the digits are identical:

$$17,\ 71,\ 26,\ 62,\ 35,\ 53,\ 44.$$So there are $\boxed{7}$ such numbers.

Answer 2

17, 26, 35, 44, 53, 62, 71, 80
I see 8 numbers

Answer 3

You are correct. The answer is indeed $\boxed{8}$. Thank you for pointing out the mistake.