Question

How many pairs of Whole numbers have a sum of 40

Answer 1

Prime #s up to 40:

2,3,5,7,11,13,17,23,29,31,37.

There are 3 pairs of prime numbers having sum of 40. The pair are {3,37},{11,29},{17,23}.

Answer 2

whole numbers are like counting numbers { 0, 1, 2,3, 4, ...} ; only positive.
since they add to make 40 there will be 40 pairs because every time you subtract one to add to the other.

40 + 0 = 40
39 + 1 = 40
38 + 2 = 40
...