Three painters can paint three walls in three minutes. how many painters are needed to paint 27 walls in nine minutes?

There is 3 variable, in this case, painters, walls and time(minutes). You need to find how many painters needed and provided information on the walls and time(minutes).

Increasing walls will cause more painter needed. It was reversed in time which was increased time will cause less painter needed.

In this case, you need to divide the variable walls with time since it reversed so: 27wall/9 minutes
It equal to : 3 walls/minute

Information provided is:
3 painters= 3 walls/3 minutes
Equal to : 3 paintes= 1 wall/minute

To make it 3 walls/minute, the painter needed will be:
(3 walls/minute) / (1 wall/minute) x 3 painters= 9 painters

9 painters

The answer is 225 miles per 4.5 hours. hope this ; )