Question

    An alloy is made of 45% lead, 35% tin, and 20% copper.

    How much lead should be added to 40 kg of the alloy so that the new alloy contains 55% lead?
    A 4 Correct Answer Incorrect Answer
    B 10 Correct Answer Incorrect Answer
    C 12 Correct Answer Incorrect Answer
    D Can’t be determined Correct Answer Incorrect Answer

    Solution

    ATQ,

    Quantity of the alloy = 40 kg

    Quantity of lead in 40 kg alloy = (0.45 × 40) = 18 kg

    Quantity of tin in 40 kg alloy = (0.35 × 40) = 14 kg

    Quantity of copper in 40 kg alloy = (0.20 × 40) = 8 kg

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

    According to the question,

    Quantity of lead in the new alloy = (Quantity of tin + Quantity of copper)

    (18 + x) = (14 + 8)

    Or, x = 22 - 18 = 4

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