Question

The ratio of boys to girls in class 7M is exactly 5:7. A new girl joins the class. The ratio of boys to girls is now 2:3. Find the number of boys and girls in the class now?

Answer 1

The number of girls i gonna ba an even number and the number of boys is in the 3 times tables

Answer 2

Say, there are an x amount of boys. Then:
7x=5y

When the girl joins, it's:
3x=2(y+1)
1.5x=y+1
1.5x-1=y

7x=5*(1.5x-1)
7x=7.5x-5
-0.5x=-5
x=10

y=7*10/5=14
14+1=15

There are 10 boys and 15 girls.