$A$ heap of rice is in the form of a cone of diameter $9 \, m$ and height $3.5 \, m$. Find the volume of the rice. How much canvas cloth is required to just cover the heap?

(N/A) Given that,a heap of rice is in the form of a cone.
Height of the cone $(h) = 3.5 \, m$.
Diameter of the cone $= 9 \, m$,so the radius $(r) = \frac{9}{2} = 4.5 \, m$.
Volume of the rice $= \frac{1}{3} \pi r^2 h = \frac{1}{3} \times \frac{22}{7} \times (4.5)^2 \times 3.5 = \frac{1}{3} \times \frac{22}{7} \times 20.25 \times 3.5 = 74.25 \, m^3$.
To cover the heap,we need the curved surface area of the cone,which is $\pi r l$,where $l = \sqrt{r^2 + h^2}$.
$l = \sqrt{(4.5)^2 + (3.5)^2} = \sqrt{20.25 + 12.25} = \sqrt{32.5} \approx 5.70 \, m$.
Curved surface area $= \frac{22}{7} \times 4.5 \times 5.70 \approx 80.61 \, m^2$.
Thus,the volume is $74.25 \, m^3$ and the required canvas cloth is $80.61 \, m^2$.