SOLUTION: Pedro can do a piece work in 4 days,while Alan can do a piece of work in 5 days. In how many days can both finish the work, if they work together?

Question 883383: Pedro can do a piece work in 4 days,while Alan can do a piece of work in 5 days. In how many days can both finish the work, if they work together?
Answer by Edwin McCravy(20055) (Show Source): You can put this solution on YOUR website!
Pedro can do a piece work in 4 days,

So Pedro's rate is

while Alan can do a piece of work in 5 days,

So Alan's rate is

In how many days can both finish the work, if they work together?

Let that be x days.

So their combined rate is 

The equation comes from:

  

  

  

Multiply through by LCD of 20x

5x + 4x = 20
     9x = 20
      x =  or  days

Edwin

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