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    Question

    Two right circular cones of equal height of radius of

    base 3cm and 4cm are melted together and made into a solid sphere of radius 5 cm. The height of the cone is.
    A 17.15cm Correct Answer Incorrect Answer
    B 18.6cm Correct Answer Incorrect Answer
    C 27.06cm Correct Answer Incorrect Answer
    D 20cm Correct Answer Incorrect Answer

    Solution

    Let the radius of two cones r1 and r2. Volume of cones = 1/3× πr2h The volume of two cones = volume of a sphere 1/3× πr12 h +1/3× πr22 h = (4/3) π ×r3 π/3×9h +π/3×16h = 4π/3 ×125 π/3[9h+16h] =4π/3 ×125 25h = 4×125 h=20cm

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