SOLUTION: last year, a farmer used 3 ploughs to plough a field in 17 hours. this year the same job must be done in 5 hours, how many ploughs will be needed?

Question 987556: last year, a farmer used 3 ploughs to plough a field in 17 hours. this year the same job must be done in 5 hours, how many ploughs will be needed?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
For last year, 1 plough would take 3
times as long, or:
1 plough plows a field in 51 hrs
51 ploughs plow a field in 1 hr
----------------------------
You only need 1/5 as many ploughs if
you want to take 5 times as long, so
plows plough the field in hrs
plows won't quite do it, they will
take hrs, so ploughs are needed

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