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

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      Log On


   

Question 143132: 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 of school.
Any help with this word problem would be appreciated.
Answer by pcsp_kumat(6) About Me  (Show Source):
You can put this solution on YOUR website!
no. of boys on first day=24
no.of girls on first day=16
total no. of students=40

solution:
let total no. of students on first day be=x
no.of boys will be=60% of x
=60*x/100
=3x/5
no.of boys after changes=75% [as no. of students remain same ]
=75%of x
=75*x/100
=3x/4
changes in boys=+6students

so [on first day]+[changes]=[after changes]
=3x/5 +6 =3x/4
=[3x+30]/5 =3x/4 [then cross multiplication]
=12x+120=15x [transposing]
=120=15x -12x
=3x =120
=x =40
on first day [boys]=60%of40=24
remaining[girls] =40% of 40 =16