The sum of the radius of the base and the height of a closed solid cylinder is 12.5 cm. If the total surface area of the cylinder is 275 cm2, then its radius is:
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Correct answer: D
Explanation
The correct answer in option 4 i.e. 3.5 cm
Total surface area of a closed cylinder = 2πRH + 2πR2
⇒ 2πR (H + R)
⇒ 275 = 2 × 22/7 × R × (12.5)
⇒ R = (275 × 7 × 10)/ 2 × 22 × 125
⇒ R = 3.5