What is the sum of the first 3 common multiples of 7 and 10?
Multiples of 7: 7, 14, 21, 28, 35, 42, 49, 56, 63, 70
Multiples of 10: 10, 20, 30, 40, 50, 60, 70
First common multiple of 7 and 10: 70
Second common multiple of 7 and 10: 2 x 70 = 140
Third common multiple of 7 and 10: 3 x 70 = 210
First 3 common multiples of 7 and 10: 70, 140, 210
Sum of the first 3 common multiples of 7 and 10
= 70 + 140 + 210
= 420
Answer(s): 420