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Surface area of sphere is ____ , when radius is r

The rate of change of surface area of a sphere of radius r when the radius is increasing at the rate of 2 cm/sec is proportional to

The radius of a sphere starts to increase at a rate of 0.1 cm/s . The rate of chane of a surface area of the sphere with time when radius is 10.

Find the surface area of sphere if radius is 9cm?

The surface area of a sphere of radius 21 cm is

The volume of a sphere is changing @ 100 cc/min. The rate at which the surface area of the sphere is changing when the radius of the sphere = 10 cm, is

Find the surface area of a sphere of radius 7 cm.