Question

A company that makes hair-care products had 9,000 people try new shampoo Of the 9,00 people, 27 had an mild allergic reaction what percent of the people had a mild allergic reaction

Answer 1

We know that out of 3000 people, 9 had a alergic reaction.
in this case our 100% is 3000, and we want to know what percentage is equivalent to those 9 that had a mild allergic reaction.
here we can use the rule of 3, this is:
if 3000 is equivalent to 100%, then 9 is equivalent to:
(9/3000)*100% = 0.3%