New SIDBI Grade A New Batch Starts on Nov 18

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    Question

    Pipe 'C' alone takes 5 more hours to fill the tank than the time taken by pipe 'C' and pipe 'D' together. Find the time taken by pipe 'C' to fill the tank alone, given that pipe 'D' alone can fill the tank in 20 hours.

    A 15 hrs Correct Answer Incorrect Answer
    B 10 hrs Correct Answer Incorrect Answer
    C 12 hrs Correct Answer Incorrect Answer
    D 18 hrs Correct Answer Incorrect Answer

    Solution

    Let the time taken by 'C' and 'D' together be 'y' hours. ATQ, On solving further we get :-

    y×(20+y+5) = 20×(y+5) 25y+y² = 20y+100 y²+5y−100 = 0 (y+10)(y−10) = 0

    Thus, y = 10 or y = −10. Discarding the negative value, y = 10. So, time taken by 'C' alone = 10 + 5 = 15 hours.

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