There are ‘b’ boys and ‘g’ girls in a class. The ratio of the number of boys to the total number of students in the class is:
Total number of students in the class are (b + g)
Hence ratio is 
9
There are ‘b’ boys and ‘g’ girls in a class. The ratio of the number of boys to the total number of students in the class is:
Total number of students in the class are (b + g)
Hence ratio is