42
19 + 21 is one pair
6
the products
260 and 7
1 and 749, when added together.
11+11
125 and 1, added together.
0 and 114 added together.
It is impossible.
0 and 49, added together.
52.5, when added together.
-174
These numbers added together make the 1000th triangle number, which is 500,500.