Problema Solution

In 

9 

hours, an experienced cook prepares enough pies to supply a local restaurant's daily order. Another cook prepares the same number of pies in 

5 

hours. Together with a third cook, they prepare the pies in 

2 

hours. Find how long it takes the third cook to prepare the pies alone.

Answer provided by our tutors

let


x = the hour the third cooks needs to prepare the pies alone


1/x pies per hour is the rate of the third cook


1/9 pies per hour is the rate of the first cook


1/5 pies per hour is the rate of the second cook


1/2 pies per hour is the rate of all three cooks together


1/x + 1/9 + 1/5 = 1/2


by solving we find:


x = 90/17


x = 5 5/17 hr


x = 5 hr (5*60)17 min


x = 5 hr 18 min approximately


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the third cook needs 5 hours and 18 minutes to prepare the pies alone.