Pierre School had 670 students and John School had 20% more students. When an equal number of students left each school, the ratio of the students in John School to that in Pierre School became 2 : 1. How many students were there in both schools in the end?

	Pierre School	John School	Difference
Before	670		134
Change	- ?	- ?
After	2 u	1 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 Pierre School and John School at first and in the end the same. 

Difference between the number of students in both schools at first
= 20% x 670
= ²⁰₁₀₀ x 670
= 134

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

1 u = 134

Total number of students in both schools in the end
= 2 u + 1 u
= 3 u
= 3 x 134
= 402

Answer(s): 402