Q15 of 292 Page 469

The radius of a sphere shrinks from 10 cm to 9.8 cm. Find approximately the decrease in (i) volume, and (ii) surface area.

Decrease in radius = dr = 10-9.8


∴ dr = 0.2


Volume of the sphere is given by =


Change in volume =


∴


⇒


Surface area of the sphere is given by =


Change in volume =


∴ dA = 8π×10× 0.2


∴ dA = 16π.


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