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datha datha
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Posts: 62
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11 years ago
A sphere and a hemisphere have the same volume. The ratio of their curved surface areas is ?
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Replies
wrote...
11 years ago
2
wrote...
11 years ago
A sphere and a hemisphere have the same volume.
The ratio of their curved surface areas is?
-----------------------------------------------------------------------


d^2 pi = 1/2 D^2 pi

factor out pi

d^2 = 1/2 D^2

divide both sides by d^2

1 = 1/2 (D^2/d^2)

multiply both sides by 2

2 = (D^2/d^2)

take the square root of both sides

sqrt(2) = D/d
Answer accepted by topic starter
nursejmnursejm
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11 years ago
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wrote...
11 years ago
Let R and r be the radius of sphere and hemishpere respectively and S and s be the surface area

Curved surface area of sphere...........S......4?R²
------------------------------------------------  = ---- = --------
Curved surface area of hemisphere....s.....½*4?r²


..S......2R²
 ---- = --------
..s........r²

Since their volumes are equal we also get  ½*(4/3)?r³ = (4/3)?R³
or r³ = 2R³  or r/R = (2)^?
=> Also from r³ = 2R³  we can say 2R²/r² = r/R, which is (2)^?
hence ratio of curved surface area of shere / hemisphere (S/s) = r/R = (2)^?  or 1.2566

or surface area of Sphere (S) = (2)^? * surface area of Hemisphere (s) of same volume
or surface area of Sphere (S) = 1.2566 * surface area of Hemisphere (s) of same volume

Hope this helped

Vick
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