Let us ask the question, "How many minutes will it take Amy to run one mile?"
If she can run 1/10 of a mile in a minute, then in ten minute she can run one mile. How? 10/10 is equal to one. In this case one mile. So, when we multiplied 1/10 by 10 we essentially added 1/10 together. Now we know Amy can run a mile in ten minutes. But what about 3 minutes? To find the answer, we simply divide 3 by 1/10.
3 / 1/10 ; Start
3 * 10/1 ; Invert 1/10
30/1 or just 30 ; Final answer