brendanbieker2
Answered

It takes Bob 18 min to set the tables in the camp dining hall. If Mary helps him, the job can be done together in 10 min. How long would it take Mary to set the tables by herself? Solve



Answer :

mhanifa

22.5 minutes

==================

Let's assume Mary's time to set the tables by herself is M minutes.

Bob's work rate is 1/18 of the job per minute.

When Bob and Mary work together, their combined work rate is 1/10 of the job per minute.

From this, we set up the equation for their combined work rate:

  • (1/18) + (1/M) = 1/10

To solve for M, follow these steps:

  • (M + 18) / (18M) = 1/10
  • 10(M + 18) = 18M
  • 10M + 180 = 18M
  • 180 = 8M
  • M = 180 / 8 = 22.5

Mary would take 22.5 minutes to set the tables by herself.