the ratio of no of boys and girls in a school was 5:3.some new boys and girls were admitted to the school in the ratio 5:7.at this the total no of students in the school became 1200,and the ratio of boys to girls changed to 7:5.the no of students in the school before new admissions were how much?

• suppose initially no. of students are x
  then no of boys = 5x/8
  no of girls = 3x/8
  
  suppose y new students added
  new no of boys 5y/12
  new no of girls = 7y/12
  
  new ratio is given 7:5
  so
  total no of boys / total no of girls = (5x/8+5y/12) / (3x/8+7y/12) = 7/5
  after solving this we get x-4y=0
  given as x+y=1200
  x=960
  new students y= 240 ans
• 6 years agoHelpfull: Yes(1) No(2)
• Ratio of
  Boys : Girls
  5a : 3a (initial students)..(i)
  5x : 7x (new joining).......(ii)
  ....................
  700 500 (total students)
  ...................
  so ,5a+5x=700 and3a + 7x= 500
  here we get a=6x
  so put value of a in ...(i)
  30x:18x......(iii)
  so boys are 30x+5x(new joining)=35x=700 ....x=20
  now put x in (iii) we get initial students= 48*20=960 students.
• 2 years agoHelpfull: Yes(0) No(0)