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    Question

    A can complete a certain work in 30 days. B is 25% more

    efficient than A and C is 20% more efficient than B. They all worked together for 3 days. B alone will complete the remaining work in:
    A 20 days Correct Answer Incorrect Answer
    B 15 days Correct Answer Incorrect Answer
    C 18 days Correct Answer Incorrect Answer
    D 12 days Correct Answer Incorrect Answer

    Solution

    A can complete the work in = 30 days Efficiency of A (A’s 1 day’s work) = 1/30 Efficiency of B (B’s 1 day’s work) = 1/30 × (125/100) = 1/24 Efficiency of B (B’s 1 day’s work) = 1/30 × (125/100) = 1/24 Efficiency of C (C’s 1 day’s work) = 1/24 × (120/100) = 1/20 Let the remaining work be complete by B in x days. According to the question, => 3(1/30 + 1/24 + 1/20) + x/24 = 1 ⇒ 3 [(4 + 5 + 6)/120] + x/24 = 1 ⇒ 15/40 + x/24 = 1 ⇒ x/24 = 1 – 3/8 ⇒ x/24 = (8 – 3)/8 ⇒ x/24 = 5/8 ⇒ x = 5/8 × 24 = 15 days

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