YAN 發問於 科學及數學數學 · 7 年前

F.2 Maths rate and ratio

Two alloys X and Y are made up of copper and zinc. Alloy X contains 37% copper

whiles alloy Y contains 50% copper.

(a) A new alloy is to be made by mixing x kg of alloy X and y kg of alloy Y. Finding

the ratio of x : y such that the ratio of copper : zinc of new alloy is at least 2 : 3.

1 個解答

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  • 7 年前
    最愛解答

    The amount of copper in the new alloy: 0.37 x + 0.5 y

    The amount of zinc in the new alloy: (1 - 0.37) x + (1 - 0.5) y = 0.63 x + 0.5 y

    Now, the required copper : zinc ratio in the new alloy is 2:3, hence:

    (0.37 x + 0.5 y) / (0.63 x + 0.5 y) = 2 / 3

    3 (0.37 x + 0.5 y) = 2 (0.63 x + 0.5 y)

    1.11 x + 1.5 y = 1.26 x + y

    0.5 y = 0.15 x

    x / y = 0.5 / 0.15

    x / y = 10 / 3

    Therefore, the ratio of x : y is 10:3

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