New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    The radii of two solid right circular cylinders are 4 cm

    and 3 cm respectively and their heights are (h+1) cm and (2h+1) cm respectively. If the areas of the whole surface of the two cylinders are equal, then the ratio of their volumes is:
    A 80:81 Correct Answer Incorrect Answer
    B 81:80 Correct Answer Incorrect Answer
    C 90:91 Correct Answer Incorrect Answer
    D 91:90 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Whole surface area of cylinder = 2πR(H+R) 2π x 4[h+1+4] = 2π x 3[2h+1+3] 4[h+5] = 3[2h+4] 4h+20 = 6h+12 2h = 8 h = 4 so, V1/V2 = (π x 42 x (h+1))/(π x 32 x (2h+1))           = (16 x (4+1))/(9 x (2x4+1))           = (16 x 5)/(9 x 9)           = 80/81

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