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    Question

    Radius of a cylindrical vessel is 3cm less than breadth

    of rectangle, while height of cylindrical vessel is equal to length of rectangle, whose area is 720 cm². If ratio between length & breadth of rectangle is 5:4, then find the thickness of 1 disc, if these discs are kept one above another in cylindrical vessel and 15 discs get completely fit in cylindrical vessel.(Let radius of discs equal to radius of cylindrical vessel)? 
    A 2 cm Correct Answer Incorrect Answer
    B 1.5 cm Correct Answer Incorrect Answer
    C 3 cm Correct Answer Incorrect Answer
    D 4 cm Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let length & breadth of rectangle be 5x & 4x respectively   Given area of rectangle = 720 cm2   5x × 4x = 720 cm2   20x2 = 720   x2 = 36   x = 6 cm Radius of cylindrical vessel = 4 × 6 − 3 = 21 cm   Height of cylindrical vessel = 5 × 6 = 30 cm    Volume of cylindrical vessel = π  × 21 × 21 × 30 = 13230 π cm3   Let thickness of each discs be x cm   So, 15 × π  × x × 21 × 21 = 13230 π cm3   x = 13230/(441 x 15) x = 2 cm

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