The ratio of boys to girls in a math club is 4:5.When 5 boys join and 2 girls leave the club, the ratio becomes 15:16. Find original number of boys and girls

Question

Could i also get a formula for working it out?

Answer 1

b-boys, g-girls.

b/g=4/5

(b+5)/(g-2)=15/16

 

So you have to solve the system of equations:

5b-4g=0

16(b+5)=15(g-2)

5b=4g

16b-15g=110

 

If you solve this, you get

b=40

g=50