The surface area of a sphere is 616 square cm

• Mensuration

The surface area of a sphere is 616 square cm. If its radius is changed so that the area gets reduced 75% then the radius becomes

1. 1.6 cm
2. 2.3 cm
3. 2.5 cm
4. 3.5 cm

Solution

Surface area of sphere = 4πr²

Area of sphere = 616

When area gets reduces 75%, new area = 154

154 = 4πr²

r = 7/2 = 3.5 cm

Correct option is D.