SOLUTION: a three person maintenance crew could clean a certain building in 4h, whereas a four person crew could do the job in 3h. if one worker of the four person crew was an hour late, how

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Question 1052638: a three person maintenance crew could clean a certain building in 4h, whereas a four person crew could do the job in 3h. if one worker of the four person crew was an hour late, how long did the job take?

Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Rate*Time=Output
Say an output of 100 makes the job complete.
.
.
.
For a 3 person crew,
R%5B3%5D%2A4=100
R%5B3%5D=100%2F4
R%5B3%5D=25
For a 4 person crew,
R%5B4%5D%2A3=100
R%5B4%5D=100%2F3
So for the first hour, it was only a 3 person crew.
25%2A1=25
So they completed 25 units of output which leaves 75 units to complete.
Now switch to the 4 person rate,
%28100%2F3%29t=75
t=%2875%2A3%29%2F100
t=9%2F4hr
So adding the hour from before,
t%5BTOT%5D=1%2B9%2F4
t%5BTOT%5D=13%2F4
t%5BTOT%5D=3%261%2F4hr