Question

Working together, Melissa and Jing can mow a lawn in 5 hours. It would take Melissa 8 hours to do the job alone.

What is the value of r, the part of the lawn that Jing could complete in 1 hour?

0.075
0.125
0.375
0.625

Answer 1

The correct answer would be: A.

Answer 2

Melissa-M
Jing-J
M-8h can finish the job so then in one hour she can finish 1/8
J-x hour can finish the job so than in one hour he can finish 1/x
(1/8 + 1/x) * 5 = 100%
5/8 + 5/x = 1
5/x = 1- 5/8 = 3/8
1/x = 3/8*1/5
1/x = 3/40 = 0.075
So r=0.075