How many 2/5 ounce doses are in 4 ounces of medicine?

In order to find the answer to this problem, you want to divide 4 by 2/5. To do this, you do the following:
Put 4 over 1, so it looks like 4/1. Now, you have the equation 2/5 * 4/1. Multiply the top by the top, and the bottom by the bottom. 2 * 4 is 8, and 5 * 1 is 5. So now you have 8/5. You don't stop here, instead  you need to make it a mixed fraction. To do that, you divide the bottom into top. 8 divided by 5 is 1, and you have 3 left over. You take that 3 and put it over 5 because before you divided, 5 was your denominator.