Question

The volume of the frustum of a cone is 690.21 m${}^3$. The bottom and top diameters are 12 m and 8 m. Find its height. (Use $\pi$ = 3). Round off your answer to nearest whole number.

• A. 9 m
• B. 10 m
• C. 5 m
• D. 8 m

Answer 1

The correct option is A 9 m

Volume of the frustum cone is $V=\frac{\pi h}{3}(R^2+Rr+r^2)$

Let us consider D is the bottom diameter and d is top diameter

D = 12 m, d = 8 m, h = ?

Volume = 690.21 m${}^3$

$Diameter=radius/2$

$R=6m$, r = 4 m

$690.21=(3\times h)/\left(3\right)[6^2+6\times 4+4^2]$

$690.21=h[36+24+16]$

$690.21=h\left[76\right]$

$h=690.21/76$

$h=9m$