By dividing by the number of minutes it takes Justin to eat 15 hamburgers, we will be able to find out how many hamburgers Justin will be able to eat in one minute.
We can do this by cross multiplying.
First we set up our equation like a ratio,
15 hamburgers / 10 minutes = x hamburgers / 1 minute
(i've provided a picture)
15/10 = 3/2 = 1.5
1.5 meaning, Justin will be able to eat 1.5 hamburgers per minute