Asked by Maria1

Dick mows the lawn in 7 hrs. Mary can do the same yard in 6 hrs. How much time would it take for them to mow the lawn together?
Answered by Reiny
Dick's rate = 1/7
Mary's rate = 1/6
combined rate = 1/7 + 1/6 = 13/42

time at combined rate = 1/(13/42) = 42/13 hrs