A right triangle with sides 3 cm, 4 cm and 5 cm is rotated the side of 3 cm to form a cone. The volume of the cone so formed is:

Answer: Option A

Solution

Answer: Option A

Solution:

$$\begin{array}{rl}& \text{Clearly},\\ & \text{We have }r=3\text{cm}\text{and}h=4\text{cm}\\ & \therefore \text{Volume}\\ & =\frac{1}{3}\pi r^{2}h\\ & =\left(\frac{1}{3}\times \pi \times 3^2\times 4\right)\text{c}{\text{m}}^3\\ & =12\pi \text{c}{\text{m}}^3\end{array}$$