Question 1014402
.Jerry washes his car in 2 hours 15 minutes. His son Timmy can wash the same car in 1 hour 25 minutes. How long it takes if they work togather?
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Jerry's rate is  1 : {{{2}}}{{{15/60}}} = 1 : {{{2}}}{{{1/4}}} = 1 : {{{9/4}}} = {{{1/((9/4))}}} = {{{4/9}}} of the car per hour.

Timmy's rate is  1 : {{{1}}}{{{25/60}}} = 1 : {{{1}}}{{{5/12}}} = 1 : {{{17/12}}} = {{{12/17}}} of the car per hour.

When they work together, their rate is {{{4/9}}} + {{{12/17}}} = {{{(4*17 + 12*9)/(9*17)}}} = {{{176/153}}} of the car per hour.

So, it will take {{{153/176}}} of an hour for Jerry and Timmy to wash the car working together.
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