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Anonymous
Anonymous asked in 科學及數學數學 · 1 decade ago

(贈送20點)..........maths

The weights of copper and zinc in an alloy are in the ratio 8:5.

a)If the alloy contains 80g of copper, how much zinc does it contain?

b)If the alloy weights 39g, what are the weights of copper and zinc in it?

2 Answers

Rating
  • ?
    Lv 7
    1 decade ago
    Favorite Answer

    a) the weight of zinc=80x5/8

    =50g

    b) the weight of copper=39x8/(8+5)

    =39x8/13

    =24g

    the weight of zinc=39x5/(8+5)

    =39x5/13

    =15g

  • 1 decade ago

    Let weight of copper = C, weight of Zine = Z

    i.e. C / Z = 8 / 5, C = (8/5)Z

    a)

    if C = 80g, then 80 = (8/5)Z

    Z = (80 x 5) / 8 = 50g

    b)

    C + Z = 39 ..... (1)

    C = (8/5)Z ...... (2)

    put (2) into (1),

    (8/5)Z + Z = 39

    (13/5) Z = 39

    Z = (39 x 5) / 13

    Z = 15 ..... (3)

    put (3) into (1)

    C = (8/5) x 15

    C = 24

    so, C = 24g and Z = 15g

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