First, we need to find the original ratio of 7th to 6th
6th = 12
7th = 21
21:12
Then find any common factors
21: 1,3,7,21
12: 1,2,3,4,6,12
divide 21 and 12 both by 3
21/ 3 = 7
12 / 3 = 4
7:4 is your ratio
For every 7 students in 7th grade, there are 4 students in 6th grade.
