Question

The volume of a cone is 1570 cm³ and its height is 15 cm. What is the radius of the cone?
(a) 10 cm
(b) 9 cm
(c) 12 cm
(d) 8.5 cm

Answer 1

(a) 10 cm
Let r cm be the radius of the cone.
Volume = 1570 cm³

$$\begin{gathered} \mathrm{Then}\frac{1}{3}\times 3.14\times r^2\times 15=1570 \\ \Rightarrow r^2=\frac{1570}{3.14\times 5}=100 \\ \Rightarrow r=10\mathrm{cm} \end{gathered}$$