Question

7. Given that w=7r+6r+5r+4r+3r. Which of the terms listed below may be added to w to the resulting sum will be divisible by 7 for every positive integer r?
A.7r
B.6r
C.5r
D.4r
E.3r

Answer 1

since w = 25r, we need to increase by 3r, making the result 28r, which is always divisible by 7, since 7 divides 28, regardless of r.

Answer 2

w=7r+6r+5r+4r+3r
w = 25r
the next multiple of 7r would be 28r for any positive integer of r
so we need to add 3r