SOLUTION: 20 men can do a piece of work in 24 days. After working for few days,4 men are added and the work was finished 3 daysearlier.After how many days were 4 men added?

Question 37839: 20 men can do a piece of work in 24 days. After working for few days,4 men are added and the work was finished 3 daysearlier.After how many days were 4 men added?
Answer by fractalier(6550) (Show Source): You can put this solution on YOUR website!
Cool problem.
We know the entire job takes 20 men 24 days to finish, or 480 man-days.
Now if we let the time they work initially to be t, we know that they worked 20t man-days. Then after the 4 men are added, they work for an additional 21 - t days, because we are told they take three days less than the original 24 days.
Okay, now if we add the two parts together, we know they must add up to the original 480 man-days...
20t + 24(21 - t) = 480
20t + 504 - 24t = 480
-4t + 504 - 480
-4t = -24
t = 6
Thus the 4 men were added after 6 days.
Good problem. I may steal that one for my students.
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