Multiple choice Find the whole surface area of a cone of base radius 21 cm and height 28cm. 3696 cm2 4442 cm2 4244 cm2 9636 cm2 Reveal answer Fill a bubble to check yourself A Correct answer Explanation Radius r = 21 cm, height h = 28 cm. Slant height l = √(r² + h²) = √(441 + 784) = √1225 = 35 cm. Total surface area = πr² + πrl = π × 21 × (21 + 35) = (22/7) × 21 × 56 = 3696 cm².