The curved surface area of a hemisphere is 72π cm2, then its radius is:

Concept: The curved (lateral) surface area of a hemisphere — only the curved dome face, excluding the flat circular base — equals 2πr2, where r is the radius. A full sphere has surface area 4πr2, and a hemisphere's curved part is exactly half of it, hence 2πr2.

Application:

1. Set up the equation 2πr2 = 72π.

2. Divide both sides by π to get 2r2 = 72.

3. Divide both sides by 2 to get r2 = 36.

4. Take the positive square root (a radius is a length): r = 6 cm.

Cross-check: Substituting r = 6 back gives 2π(62) = 2π × 36 = 72π cm2, which matches the given curved surface area, confirming the radius is 6 cm.