Question 1052638
Rate*Time=Output
Say an output of 100 makes the job complete.
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For a 3 person crew,
{{{R[3]*4=100}}}
{{{R[3]=100/4}}}
{{{R[3]=25}}}
For a 4 person crew,
{{{R[4]*3=100}}}
{{{R[4]=100/3}}}

So for the first hour, it was only a 3 person crew.
{{{25*1=25}}}
So they completed 25 units of output which leaves 75 units to complete.
Now switch to the 4 person rate,
{{{(100/3)t=75}}}
{{{t=(75*3)/100}}}
{{{t=9/4}}}{{{hr}}}
So adding the hour from before,
{{{t[TOT]=1+9/4}}}
{{{t[TOT]=13/4}}}
{{{t[TOT]=3&1/4}}}{{{hr}}}