Fung 發問於 科學及數學數學 · 1 十年前

(emergency) maths equation form 1

mary and ann will finish a piece of work in 3 days.Mary alone will finish it in 5days.How many days will Ann need to finish the work by herself?

please in detail

thank you

1 個解答

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  • 1 十年前
    最愛解答

    Let the speed of mary is x piece per day, the speed of ann is y piece per day. Total speed is (x+y) piece per day

    Then we have

    3(x+y)=1 (total work 1 piece)

    On the other hand

    Mary alone will finish it in 5days. So

    5x=1

    Then

    3(x+y)=5x

    3y=2x

    y=(2/3)x

    From 5x=1, x=0.2. y is 2/15

    The speed of ann is 2/15 piece per day

    The days Ann need to finish the work by herself

    =1/(2/15)

    =15/2

    =7.5 days

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