There are 400 students in a school. Fifty-five percent are girls. How many boys are there?

Question

What are the steps for solving this type of percent problem?

Answer 1

Percents may be written as:

   55%  or   (55/100)    or 0.55    as needed by the problem.

 

Assuming that you have girls and boys,

   number of girls       +      number of boys         =      400

     (55/100)(400)      +      number of boys         =      400       ["of" usually means multiply; percent "of"]

 

           220 + number boys = 400

           number of boys = 400 - 220      [subtract 220 from both sides]

             number of boys = 180

 

Also note that 100% - 55% leaves 45%.   So, 45% are boys.

      (45/100)400 = 180