Multiple choice

The lateral surface area of a right circular cone of height 28 cm and base radius 21 cm is

  1. 1155 cm2

  2. 1055 cm2

  3. 2110 cm2

  4. 2310 cm2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Lateral surface area of a cone = pi * r * l, where l = sqrt(r^2 + h^2). l = sqrt(21^2 + 28^2) = sqrt(441 + 784) = sqrt(1225) = 35. Area = (22/7) * 21 * 35 = 22 * 3 * 35 = 2310 cm^2.

AI explanation

First find the slant height using the Pythagorean theorem: l = the square root of (21 squared + 28 squared), which gives l = 35 cm. The lateral surface area of a right circular cone is pi times radius times slant height. Calculating 22 divided by 7 times 21 times 35 yields 2310 cm2.

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