Question

Working together, Edward and Frances can wallpaper an apartment in 12 hours. It would take Frances 30 hours to do the same job by herself. How long would it take Edward to do it alone?

Answer 1

Answer:

Step-by-step explanation:

Givens

together: 12 hours

Frances: 30 hours

Edward: x

Formula

The formula is an odd one that shows up in physics as well.

1/Frances + 1 / Edward = 1/Together.

Solution

1/30 + 1/x = 1/12

LCD for 12 and 30

12: 2 * 2 * 3

30:3 * 2 * 5

LCD: 2*2*3*5

LCD: 60

2/60 + 1/x = 5/60               Subtract 2 / 60 from both sides

1/x = 5/60 - 2/60

1/x = 3/60                           Cross Multiply

3x = 60*1                            Divide by 3

3x/3 = 60/3

x = 20

So Edward (doing it alone) takes 20 hours to do the job.