Let A be the set of all composites less than 10, and B be the set of positive even integers less than 10. How many different sums of the form a + b are possible if a is in A and b is in B? A = {4,6,8,9} B = {2,4,6,8} Make an addition table: + A 4 6 8 9 B ——————————————— 2 | 6 8 10 11 | 4 | 8 10 12 13 | 6 | 10 12 14 15 | 8 | 12 14 16 17 The different sums are 6, 8, 10, 11, 12, 13, 14, 15, 16, 17 So there are 10 different sums. Edwin