Question

    An alloy consists of 35% gold, 40% silver, and 25% copper.

    How much gold should be added to 20 kg of the alloy so that the new alloy contains 50% gold?
    A 4 Correct Answer Incorrect Answer
    B 10 Correct Answer Incorrect Answer
    C 12 Correct Answer Incorrect Answer
    D 6 Correct Answer Incorrect Answer

    Solution

    ATQ,

    Quantity of the alloy = 20 kg

    Quantity of gold in 20 kg alloy = (0.35 × 20) = 7 kg

    Quantity of silver in 20 kg alloy = (0.40 × 20) = 8 kg

    Quantity of copper in 20 kg alloy = (0.25 × 20) = 5 kg

    Let the quantity of gold to be added be x kg.

    According to the question,

    Quantity of gold in the new alloy = (Quantity of silver + Quantity of copper)

    (7 + x) = (8 + 5)

    Or, x = 13 - 7 = 6

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