If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?

The key is start out by working out the number of widgets per minute that a single machine makes. If it takes five minutes for five machines to produce five widgets then, on average, it takes five machines 1 minute to make one widget, and hence, on average, one machine makes 0.2 widgets per minute. To calculate how long it would take 1 machine to produce 100 widgets we divide 100 by 0.2 to get 500 minutes. And therefore to work out how much time it takes for 100 machines to produce 100 widgets we divide 500 by 100 to get 5minutes.