Question

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

Answer 1

1) 55% is girls, then 
100-55=45% is boys.

2) 45%=0.45                                     or  2) 400 ----100%
3)400*0.45= 180 boys                                 x -----45%      x=400*45/100=180 boys

Answer is 180 boys.