water tank open at the top is hemi spherical at the bottom and cylindrical above it The radius is 12...........

Quantitative Aptitude (CDS) Mensuration 3D

water tank, open at the top, is hemi-spherical at the bottom and cylindrical above it. The radius is 12 m and the capacity is 3312π m³. The ratio of the surface areas of the spherical and cylindrical portions is

3 : 5

4 : 5

1 : 1

6 : 5

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Explanation:

Let the height of the cylinder be h m.
Radius of the cylinder = Radius of the hemisphere = r = 12 m
∴2/3π×12³+π×12²×h=3312π
⇒8+h=3312/144=2323
⇒h=15m
Therefore, ratio of the surface areas of the spherical and cylindrical portions

=2πr²:2πrh=r:h=12:15=4:5