Question

The ratio of number of boys to the number of girls in a school of 1440 students is 7:5.If 40 new boys are admitted,find how many new girls may be admitted to make this ratio 4:3

Answer 1

Let the no. of boys$=7x$

No. of girls$=5x$

$7x+5x=144012x=1440\Rightarrow x=120$

$\therefore$ No. of boys$=120\times 7=840$

No. of girls$=5\times 120=600$

Let $y$ be the no. of girls to be added

$\Rightarrow \frac{4}{3}=\frac{840+40}{600+y}\Rightarrow 2400+4y=3320+120\Rightarrow 4y=3440-2400=1040\Rightarrow y=\frac{1040}{4}=260$

$\therefore$ no. of girls that needs to be added $=260$