A cylindrical concrete pier is 3 ft in diameter and 12 ft deep. Using pi = 3.1416, what is the MINIMUM volume of concrete required to fill it?

Giải thích

Volume of a cylinder = pi x r^2 x h. The radius is half the diameter, so r = 1.5 ft. V = 3.1416 x 1.5^2 x 12 = 3.1416 x 2.25 x 12 = about 84.8 cu ft. Option c (42.4) is half the correct value. Option d (339.3) wrongly uses the diameter (3 ft) as the radius. Option b confuses the formula factors. Always square the radius, not the diameter.