Find the radius of a sphere whose surface area is 154 cm².

Surface area of sphere is 154 cm². Let the radius of sphere = r cm
surface area of sphere = 4πr²
⇒ 154 = 4 × 22/7 × r² ⇒ r² = 154 × 7/22 × 1/4 ⇒ r² = 77/4 ⇒ r = √77/4 = 7/2
Hence, the radius of sphere is 7/2 cm.