How many pairs of whole numbers have a sum of 99?

With the sum of 99, we will get 50 pairs whole numbers. Why?

Let’s start with

0 + 99

1 + 98

2 + 97

3 + 96

4 + 95

5 + 94

6 + 93

7 + 92

8 + 91

9 + 90

10 + 89

...

...

43 + 49

44 + 50

Therefore, if you’re going to count all pairs of whole number, you will get 50 pairs of whole number with the sum of 99.