Find the radius of a sphere whose surface area is 154 cm2.
Let r be the radius of the sphere. Surface area = 154 cm2 ⇒ 4πr2 = 154 ⇒ 4 × 22/7 × r2 = 154 ⇒ r2 = 154/(4 × 22/7) ⇒ r2 = 49/4 ⇒ r = 7/2 = 3.5 cm
