A solid brass sphere of radius 2.1 dm is converted into a right circular cylindrical rod of length 7cm. The ratio of total surface areas of the rod to the sphere is
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 7 : 3
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Understanding |
Application |
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A solid brass sphere of radius 2.1 dm is converted into a right circular cylindrical rod of length 7 cm. |
So, 4/3 × π × (2.1 × 10)3 = π × r2 × 7 r2 = 2 × 2 × 21 × 21 r = 42 cm |
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Total surface areas of the cylinder = 2πrh + πr2 Total surface areas of the sphere = 4πR2 |
So, Required ratio = (2πrh + πr2) : 4πR2 = [2 × 42 × (42 + 7)] : [4 × 21 × 21] = 49 : 21 = 7 : 3 |