SOLUTION: A window washer can wash the windows on one side of a building in 72 working hours. With an assistant he can do the job in 40 hours. How many hours would the assistant take to do t

Question 336947: A window washer can wash the windows on one side of a building in 72 working hours. With an assistant he can do the job in 40 hours. How many hours would the assistant take to do the job working alone?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A window washer can wash the windows on one side of a building in 72 working hours.
W W DATA:
time = 72 hrs/job
rate = 1/72 job/hr
----------------------------
With an assistant he can do the job in 40 hours.
Together DATA:
time = 40 hrs/job
rate = 1/40 job/hr
----------------------
Assistant DATA:
time = x hrs/job
rate = 1/x job/hr
-----------------------
How many hours would the assistant take to do the job working alone?
Equation:
rate + rate = together rate
1/72 + 1/x = 1/40
----
Multiply thru by 40*72x to get:
40x + 40*72 = 72x
32x = 40*72
x = 90 hrs (time the assistant would need to do the job alone)
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Cheers,
Stan H.
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