Find the volume of a right circular cone that has a height of 12.4 in and a base with a diameter of 15.6 in. Round your answer to the nearest tenth of a cubic inch.

Answer 1

V = (1/3)(π)(7.8)²(12.4)

Answer 2

V = (1/3)πr²h = (1/3)π(15.6/2)²(12.4) = (1/3)π(7.8)²(12.4) ≈ 790 cubic inches

The radius is half of the diameter, so this is where 15.6/2 = 7.8 comes from