SOLUTION: On the first day of school, the percentage of boys in a particular class is 60%. During the school year,six girls move away, and are replaced in the class by six boys, this makes t

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: On the first day of school, the percentage of boys in a particular class is 60%. During the school year,six girls move away, and are replaced in the class by six boys, this makes t      Log On


   

Question 477900: On the first day of school, the percentage of boys in a particular class is 60%. During the school year,six girls move away, and are replaced in the class by six boys, this makes the class roster 75% boys. Find the number of boys and girls in the class on the first day.

I am completely lost on this one.
Answer by mangopeeler07(462) About Me  (Show Source):
You can put this solution on YOUR website!

Set B for the number of boys on the first day. Set G for the number of girls.
so B%2BG=A (A for all), where B=.6A (sixty percent).


Six girls move
G-6


and six boys come
B%2B6


And now the boys make up 75% of the class
B%2B6=.75A


Using B=.6A and B%2B6=.75A, plug in .6A for B:
.6A%2B6=.75A


Subtract .6A from both sides:
6=.15A


Now divide both sides by .15
40=A


So there were 40 kids in all on the first day. 60% of them were boys, so:
.6%2840%29=B
24=B


40-24=G
G=16


So on the first day of school, there were 24 boys and 16 girls.