Question

It takes Noah 3 hours to paint one side of a fence. It takes Gilberto 5 hours. How long would it take them if they worked together?

Answer 1

I tried this but check it.

Explanation:

Let us say that the rates at which each one paints the surface (of area `1` for example) are:
`1/3` and `1/5` to paint the same surface so together they will need a time `t`:
`1/3t+1/5t=1`
rearranging:
`5t+3t=15`
`8t=15`
`t=15/8=1.875` less than 2 hours.