Question

The volume of the frustum of a cone is 7,740 cm${}^3$. The bottom and top radius are 14 cm and 7 cm. Find its height. (Use $\pi$ = 22/7). Round off your answer to nearest whole number.

• A. 21 cm
• B. 22 cm
• C. 23 cm
• D. 24 cm

Answer 1

The correct option is B 22 cm

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

$R=14cm,r=7cm,h=?$

$Volume=7,740cm$${}^3$

$7,740=(22\times {/}^{\prime }h)/(7\times 3)[{14}^2+14\times 7+7^2]$

$7,740\times 21=22\times h[196+98+49]$

$\frac{162,540}{22}=h\left[343\right]$

$\frac{7,388.18182}{343}=h$

$h=22cm$