Billy School had 620 students and Fred School had 10% more students. When an equal number of students left each school, the ratio of the students in Fred School to that in Billy School became 3 : 2. How many students were there in both schools in the end?

	Billy School	Fred School	Difference
Before	620		62
Change	- ?	- ?
After	3 u	2 u	1 u

Since an equal number of students left each school, the difference in the number of students at first and in the end between the 2 schools remains the same.  Make the difference between the number of students in Billy School and Fred School at first and in the end the same. 

Difference between the number of students in both schools at first
= 10% x 620
= ¹⁰₁₀₀ x 620
= 62

Difference between the number of students in both schools in the end
= 3 u - 2 u
= 1 u

1 u = 62

Total number of students in both schools in the end
= 3 u + 2 u
= 5 u
= 5 x 62
= 310

Answer(s): 310