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Question
In a hollow cylinder, the sum of the external and internal radii is 14 cm and the width is 4 cm. If its height is 20 cm, the volume of the material in it is
Options
5600π cm3
11200π cm3
56π cm3
3600π cm3
Solution
11200π cm3
Explanation;
Hint:
Here, let the external radius be "R" and the internal radius be "r"
R + r = 14 ...(1)
Width (R – r) = 4 ...(2)
Height of the hollow cylinder = 20 cm
Volume of the hollow cylinder = πh × (R2 – r2)
= πh(R + r) (R – r)
= π × 20 (14) × 4
= π × 1120
= 1120π cm3
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