Sherry can paint her backyard fence by herself in 5 hours. If she invites her friend Amy over to help, they are able to complete the same job in 3 hours. How long would it take if Amy offers to paint the fence alone?

Respuesta :

It will take Amy 7.5 hours to paint the fence alone

Reciprocal of a function:

Let the time taken by Amy offers to paint the fence alone be x

If Sherry can paint her backyard fence by herself in 5 hours and they can both complete it in 3 hours, then;

  • 1/3 = 1/x + 1/5

Solve for x;

1/x = 1/3 - 1/5

1/x = 5-3/15

1/x = 2/15

x = 15/2

x = 7.5 hours

Hence it will take Amy 7.5 hours to paint the fence alone

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