SOLUTION: 40% of the student in a school are girls.If the total number of girls in the school is 420. Find the number of student in the school. Also, find the of boys in the school.

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: 40% of the student in a school are girls.If the total number of girls in the school is 420. Find the number of student in the school. Also, find the of boys in the school.      Log On


   

Question 1115591: 40% of the student in a school are girls.If the total number of girls in the school is 420. Find the number of student in the school. Also, find the of boys in the school.
Found 2 solutions by Fombitz, MathTherapy:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
%2840%2F100%29%28G%2BB%29=G
and
G=420
.
.
40%28420%2BB%29=100%28420%29
16800%2B40B=42000
40B=25200
Solve for B, then solve for B%2BG

Answer by MathTherapy(10555) About Me  (Show Source):
You can put this solution on YOUR website!

40% of the student in a school are girls.If the total number of girls in the school is 420. Find the number of student in the school. Also, find the of boys in the school.
Just use a proportion, as follows: highlight_green%28matrix%281%2C3%2C+.4%2F1%2C+%22=%22%2C+420%2FS%29%29, with S being the number of students in the school. Solve this for S.

I think you should be able to find out how many boys there are, considering that you already know the total number of students (S) as well as the number of girls.