Question 143132
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