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Math Help - Rational Equation to solve work problem.

  1. #1
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    Rational Equation to solve work problem.

    One group of construction workers can build a skyscraper in 240 days. Another group of construction workers can build the same skyscraper in 180 days. How long will it take them to build three of these same skyscrapers if the two groups work together?

    No clue how to work out the above. TIA!
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  2. #2
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    Quote Originally Posted by eagertolearn View Post
    One group of construction workers can build a skyscraper in 240 days. Another group of construction workers can build the same skyscraper in 180 days. How long will it take them to build three of these same skyscrapers if the two groups work together?

    No clue how to work out the above. TIA!
    Work done by group 1 in a day = (1/240)th portion of the work
    Work done by group 2 in a day = (1/180)th portion of the work

    Now if they work together, the work done by both the group will be added,
    i.e. total work done in 1 day by both group = [(1/240) + (1/180)] part of the work.
    = [(3+4)/720] = (7/720)th part of work.

    time required to complete the work = 720/7 days = 102.86 day.

    well, that was the complete solution!
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  3. #3
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    Hello everyone
    Quote Originally Posted by annran View Post
    Work done by group 1 in a day = (1/240)th portion of the work
    Work done by group 2 in a day = (1/180)th portion of the work

    Now if they work together, the work done by both the group will be added,
    i.e. total work done in 1 day by both group = [(1/240) + (1/180)] part of the work.
    = [(3+4)/720] = (7/720)th part of work.

    time required to complete the work = 720/7 days = 102.86 day.

    well, that was the complete solution!
    Don't forget to multiply this answer by 3, since three skyscrapers were required!

    Grandad
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  4. #4
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    Quote Originally Posted by Grandad View Post
    Hello everyoneDon't forget to multiply this answer by 3, since three skyscrapers were required!

    Grandad
    Yes, I forgot to multiply by 3!
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  5. #5
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    Thank you annran and grandad!
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