if one machine can do a piece of work in 10 hours and a second machine can do the same work in 15 hours, how many hours will it take both machines simultaneously to do the work?

Question

A) 12.5
B) 25
C) 5
D) 6

Answer 1

1/10 + 1/15 = 1/x
solve for x

Answer 2

its 25