Question

To do a job alone, it would take Peter 2 hours, John 4 hours and Paul 6 hours. How long would it take them to finish the job if they work together? ​

Answer 1

Answer:

We know that

J + K + L = 1/2 (working together for an hour, they can do half the job)

J = 1/5 (working alone, Jane does 1/5 of the job in an hour)

K = 1/6 (working alone, Paul does 1/6 of the job in an hour)

1/5 + 1/6 + L = 1/2

6/30 + 5/30 + L = 15/30

L = 4/30 = 2/15

Working alone, Peter can paint 2/15 of the fence in an hour, so it would take him 15/2 = seven-and-a-half hours to paint the fence by himself.