If the radius of a cylinder opens at both the ends, is decreased by 25%, and the height of the cylinder is increased by 25%. Then the curved surface area of the cylinder thus formed
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. is decreased by 6.25%.
| Application |
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Let the radius of the original cylinder = r cm and the height = h cm. Surface area of cylinder = 2πrh New radius after decrease =75r/100 = 0.75r New height after increase = 125h/100 = 1.25h The new surface area of the cylinder = 2π × 0.75r × 1.25h = 1.875πrh. Since, 1.875 < 2, the surface area has decreased. %decrease = (original surface area - New surface area)/original surface area × 100 = (2πrh - 1.875)/2πrh × 100 = (0.125/2) × 100 = 6.25%. |