A solid consists of a cone on top of a cylinder with a radius equal to that of the cone. The height of the cone is 12 12 and the height of the cylinder is 24 24. If the volume of the solid is 42 pi42π, what is the area of the base of the cylinder?

1 Answer
Aug 4, 2018

color(maroon)("Cylinder base area " = A = 3/2 pi " sq units"Cylinder base area =A=32π sq units

Explanation:

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"Volume of cone " V_(cone) = 1/3 pi r^2 h_1Volume of cone Vco=13πr2h1

"Volume of cylinder " V_(cyl) = pi r^2 h_2Volume of cylinder Vcyl=πr2h2

"Volume of solid " V = 1/3 pi r^2h_1 + pi r^2 h_2 = pi r^2 (1/3 h_1 + h_2)Volume of solid V=13πr2h1+πr2h2=πr2(13h1+h2)

"Area of cylinder base " = A = pi r^2Area of cylinder base =A=πr2

"Given " V = 42 pi, h_1 = 12, h_2 = 24, pi r^2 = ?Given V=42π,h1=12,h2=24,πr2=?

pi r^2 (1/3 h_1 + h_2) = 42 piπr2(13h1+h2)=42π

pi r^2 = (42 pi) / (1/3 h_1 + h_2)πr2=42π13h1+h2

A = pi r^2 = (42 pi) / (1/3 * 12 + 24) = (42 pi) / 28A=πr2=42π1312+24=42π28

color(maroon)(A = 3/2 pi " sq units"A=32π sq units