Question

A skin-care company had 1,500 people try a new acne cream. Nine people had a mild allergic reaction. The formula is then improved and those 1,500 people try the new cream. Only 4 of them had a mild allergic reaction. What is the percent decrease in number of allergic reactions?

Answer 1

The decrease in number of allergic reactions is of 0.3333%.

Explanation:

Initial percentage:

Nine out of 1500, so the percentage is:

`(9*100)/(1500) = (900)/(1500) = 0.6`

Initially: 0.6% of allergic reactions.

Final percentage:

Four out of 1500, so the percentage is:

`(4*100)/(1500) = (400)/(1500) = 0.2667`

WIth the improved formula: 0.2667% of allergic reactions.

What is the percent decrease in number of allergic reactions?

0.6% - 0.2667% = 0.3333%

The decrease in number of allergic reactions is of 0.3333%.