Question

Find the volume of the frustum cone whose base and top
radius is 21 in and 5 in respectively. The height of the cone is 300 in. (Use $\pi$ = 3).

• A. 181,300 in${}^3$
• B. 171,300 in${}^3$
• C. 161,300 in${}^3$
• D. 151,300 in${}^3$

Answer 1

The correct option is B 171,300 in${}^3$

Volume of the frustum cone is $V=\frac{\pi h}{3}(R^2+Rr+r^2)$
$R=21ft,r=5ft,h=300ft$
$V=(3\times 300)/\left(3\right)[{21}^2+21\times 5+5^2]$
$=300[441+105+25]$
$=300\left[571\right]$
$=$ 171,300 in${}^3$