Question

The volume of frustum of a cone is 3,600 cm${}^3$. The area of the bottom circle of the cone is 4 cm${}^2$ and the area of the top circle of the cone is 16 cm${}^2$. Find its height.

• A. 385.7 cm
• B. 375.7 cm
• C. 365.7 cm
• D. 355.7 cm

Answer 1

The correct option is A 385.7 cm

Volume of the frustum cone is V = $\frac{h}{3}[A_1+A_2+\sqrt{A_1{A}_2}$]

Area of the bottom cone, $A_1=4c{m}^2$

Area of the top cone, $A_2=16c{m}^2$

Height = ?

Volume = 3,600 cm

$3,600=h/3[4+16+\sqrt{4\times 16}]$

$3,600\times 3=h[20+\sqrt{64}]$

$10,800=h[20+8]$

$10,800/28=h$

$h=385.7cm$