How many pairs of whole numbers have a sum of 40
So,We start with 0 + 40.1. 0 + 402. 1 + 393. 2 + 384. 3 + 37.........19. 18 + 2220. 19 + 2121. 20 + 20Tada! There are 21 pairs of whole numbers that have a sum of 40.