Kerala Board Solutions for Chapter: Solids, Exercise 7: Exercise 7

What is the area of the curved surface $\left({\mathrm{cm}}^2\right)$ of a cone of base radius $12$ centimetres and slant height $25$ centimetres?

What is the surface area of a cone of base diameter $30$ centimetres and height $40$ centimetres?
(Note: Consider $\mathrm{\pi }=\frac{22}{7}$)

A conical fire work is of base diameter $10$ centimetres and height $12$ centimetres. $10000$ such fireworks are to be wrapped in colour paper. The price of the colour paper is $2$ rupees per square metre. What is the total cost? Use the $₹$ symbol and take $\mathrm{\pi }=3.14$.

Prove that for a cone made by rolling up a semicircle, the area of curved surface is twice the base area.