SOLUTION: A contractor agrees to lay a road 3000 m long in 30 days. 50 men are employed and they work for 8 hours per day. After 20 working days, he finds that only 1200 m of the road is co

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Question 1078849: A contractor agrees to lay a road 3000 m long in 30 days. 50 men are employed and they work for 8 hours per day. After 20 working days, he finds that only 1200 m of the road is completed. How many more men does he need to employ in order to finish the project on time if each man now works 10 hours a day?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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A contractor agrees to lay a road 3000 m long in 30 days.
50 men are employed and they work for 8 hours per day.
After 20 working days, he finds that only 1200 m of the road is completed.
How many more men does he need to employ in order to finish the project on time if each man now works 10 hours a day?
:
Find how many man-hrs needed to complete 1200 meters
50 * 8 * 20 = 8000 man-hrs
Find how many man-hrs per meter
8000/1200 = 6.67 man-hr per meter
then find how many for the remaining 1800 meters
6.67 * 1800 = 12000 man-hr required to complete the job
:
let m = the additional men required working 10 hrs a day for the 10 days left on the contract
(50+m) * 10 * 10 = 12000
100(50+m) = 12000
50 + m = 12000/100
50 + m = 120
m = 120 - 50
m = 70 additional men required