Question 1208470
<font color=black size=3>
Answer: <font color=red>80 days</font>


Explanation


Consider a warehouse with 72000 boxes. 
There are 72 men who can move these boxes in 100 days. 
Assume that none of the workers hinder one another. 
Each man would move 72000/72 = 1000 boxes.
Each man has a unit rate of 1000/100 = 10 boxes per day.


1 man can move 10 boxes per day.
80 men can move 80*10 = 800 boxes per day.
Over the course of 40 days, that would be 800*40 = 32000 boxes.
There are 72000-32000 = 40000 boxes remaining.


The 80-man crew drops to 50 since 30 people transfer.
x = number of days to move 40,000 boxes
1 man can move 10 boxes per day
50 men can move 50*10 = 500 boxes per day
500x = number of boxes to move
500x = 40000
x = 40000/500
x = <font color=red>80</font>
</font>