In a class, the number of girls is 20% more than that of the boys. The strength of the class is 66. If 4 more girls are admitted to the class, the ratio of the number of boys to that of the girls is :

20% = $$\frac{1}{5}$$ = $$\frac{{6\,\, \to \,\,{\text{Girls}}}}{{5\,\, \to \,\,{\text{Boys}}}}$$
Boys : Girls
5 : 6
According to the question,
(5 + 6) units = 66
11 units = 66
1 unit = 6
Hence Boys = 6 × 5 = 30
           Girls = 6 × 6 = 36
The number of girls when 4 is admitted
= (36 + 4)
= 40
Required ratio :
= 30 : 40
= 3 : 4