Question

There are 20 identical solid hemispheres. The curved surface and the flat surface of each hemisphereare are to be painted red and yellow respectively. Find the ratio of the amount of red paint needed to the amount of yellow paint needed.​

Answer 1

2:1.

Explanation:

The area of a red curved surface = 2πr^2.

The area of the yellow flat surface = πr^2.

This is the case for all the hemispheres.

Therefore the required ratio = 2πr^2 : πr^2

= 2:1.