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    Question

    A meter-long pipe is made whose internal diameter is equal to the outer radius. How much material (cubic units) will be required to make the pipe if it holds 88/7m³?

    A 37.7m³ Correct Answer Incorrect Answer
    B 35.5m³ Correct Answer Incorrect Answer
    C 33.3m³ Correct Answer Incorrect Answer
    D 36.5m³ Correct Answer Incorrect Answer

    Solution

    Let the radius of the inner cylinder be r and the radius of the outer cylinder be R. 2r = R  In this figure, the amount of water that will flow will be equal to the volume of the inner cylinder. The volume of cylinder = πr2h 88/7 =  22/7 ×1× r2 r  = 2 , then R = 4 Materials used to make pipe (volume) = volume of outer cylinder - volume of the inner cylinder = πR2h-πr²h V = πh (R2  -r2  ) V = 22/7 ×1×(16-4) V =  22/7 ×1×12 V = 37.7 m³ 

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