A cosmetics company tested a new lotion. Of the 2,500 people tested, 15 had an allergic reaction. What percent of the people tested had an allergic reaction to the new lotion

If we want to know what percent of a number A is of another number B, then all we have to do is to simply divide number A by number B. Then either we move the decimal place of the answer two places to the right or multiply the answer with 100, either method results in the same number.

So the percent of tested people who had an allergic reaction to the new lotion is:

percent people = (15 / 200) * 100

percent people = 0.075 * 100

percent people = 7.5%

Therefore 7.5% of the people had allergic reaction.