Question

A tin of paint covers a surface area of 70m².

Each tin costs £5.20.
The entire surface of a solid cylindrical rod with diameter 7m and height 13m needs to be
painted.
Find the minimum cost of painting the rod.

Answer 1

£25.53

Explanation:

The surface area of a cylinder is 2πr^^2+2πrh, where r is the radius and h is the height.

In this case, the radius is 3.5 m and the height is 13 m, so the surface area is 2π(3.5)^2+2π(3.5)(13)=245.5 m^2

Each tin of paint covers 50 m$^2$, so we need

245.5/50​ =4.91 tins of paint. Each tin costs £5.20, so the total cost of the paint is 4.91×£5.20=£25.53.

Therefore, the minimum cost of painting the rod is £25.53.