Question

the ratio of girls to boys in a school is 2:7. if the number of boys is 630, find the number of girls in the school

Answer 1

Answer:

Let the number of boys be 3x

Then the number of girls =2x

∴3x+2x=630

⇒5x=630∴x=126

⇒ number of boys =3x=3×126=378

And number of girls =2x=2×126=252

After admission of 90 students we have total number of students =630+90=720

Now, let the number of boys be 7x

Then, the number of girls =5x

∴7x+5x=720

⇒12x=720

∴x=60

⇒ number of boys =7x=7×60=420

And number of girls =5x=5×60=300

∴ Number of newly admitted boys =420−378=42