LM wrote:
What is the sum of the multiples of 7 from 84 to 140, inclusive?
A. 896
B. 963
C. 1008
D, 1792
E. 2016
A. 896
B. 963
C. 1008
D, 1792
E. 2016
Alternatively, note that 84 = 7*12 and 140 = 7*20
7*12 + 7*13 + ... 7*20 = 7*(12 + 13 + 14 .. + 20)
12 to 20 are 9 consecutive numbers so their sum will be (middle number) * 9 = 16*9 = 144
Total sum = 7*144 = 1008