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    Question

    Alloy A contains copper and zinc in the ratio 4:5 and

    alloy B contains copper and zinc in the ratio 7:2. A and B are taken in the ratio 7:4 and melted to form a new alloy. The percentage of zinc in the new alloy is closest to: 
    A 43% Correct Answer Incorrect Answer
    B 57% Correct Answer Incorrect Answer
    C 25% Correct Answer Incorrect Answer
    D 79% Correct Answer Incorrect Answer

    Solution

    Alloy A (Copper:Zinc = 4:5) Total parts = 4 + 5 = 9 Copper fraction = 4/9, Zinc fraction = 5/9 Alloy B (Copper:Zinc = 7:2) Total parts = 7 + 2 = 9 Copper fraction = 7/9, Zinc fraction = 2/9 Mixing A and B in ratio 7:4 Assume we take 7x of A and 4x of B. Find total copper and zinc in the mixture

    Total mass = Copper + Zinc = 11x Zinc % = 43/99 × 100 = 43.43% The percentage of zinc in the new alloy is 43% (approx).

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