Question

Amir wants to do a full painting on the surface of a pottery. The pottery is in the shape of a cylinder with a height of 14 cm and a radius of 4.5 cm. If one tube of colour can be used to paint 120 cm² of drawing, calculate the number of tubes of colour needed to paint 15 potteries of the same type.​

Answer 1

About 66 tubes

Explanation:

Cylinder surface area formula: 2πr(h + r) where h = height and r = radius

In this case, h = 14, π = 3.14 and r = 4.5 so the surface area of one pottery is:

2 * π * 4.5 * (14 + 4.5) = 166.5π ≈ 523.08

The surface area of 15 potteries would be 523.08 * 15 = 7846.2 so it would take 7846.2 / 120 = 65.385 ≈ 66 tubes. We round to the nearest integer because in this context, you can only have integer values of tubes, you can't have, say, 0.5 tubes.