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Math Help - please help about ratio and proportion

  1. #1
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    please help about ratio and proportion

    Q1- A Contractor agree to lay a road 3000m long in 30 days. He employs 50 men who work for 8 hours a day. After 20 working days, he finds that only 1200m of the road is completed. How many more men should he employ to finish the work on time if each man now works 10 hours a day?

    Q2- To paint a house john takes 6 days, peter takes 4 days and Paul takes 12 days. How many days will they take if they work together?

    Q3- Three pipes fill a swimming pool in half an hour. If two of them take 1.5 hours and 1.3333 hours respectively to fill it alone. How many hours will the third pipe take to fill it alone?
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by ea12345 View Post
    Q1- A Contractor agree to lay a road 3000m long in 30 days. He employs 50 men who work for 8 hours a day. After 20 working days, he finds that only 1200m of the road is completed. How many more men should he employ to finish the work on time if each man now works 10 hours a day?
    50 men 8 hours a day for 20 yays is 50x8x20=8000 man hours to lay 1200m of road. that gives 8000/1200=6.666.. mam hours to lay 1m.

    There are 1800 m still to lay, that will require 12000 man hours over 10 days = 80 hours. So 12000/80=150 men will be needed, which is an extra 100 men.

    CB
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  3. #3
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    No its Answer is 70 men
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  4. #4
    Grand Panjandrum
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    Quote Originally Posted by ea12345 View Post
    No its Answer is 70 men
    No, that is the answer in your book, and it may be wrong, or you may have looked it up incorrectly, or ...

    If the answer were 70 that would mean you had 120 men or 2.4 as many as before, so in 20 days the would lat 1200x2.4=2880m of road, or in the 10 remaining days 1440m of road. So in total 1200+1440=2640m of road would have been laid not the 3000m required. Alternativly I could be wrong.

    CB
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