Solution: suppose there are x boys and y girls;

4x+3.25y=(x+y)×3.6

Simplify and get 0.4x=0.35y

x:y = 7:8；

7+8= 15

15×2=30; 15×3=45、 15×4=60;

Also, 30

Therefore, for boys, x = 45× 7/15 = 21;

Girls y=45×8/ 15=24.