Archie School had 640 students and Flynn School had 30% less students. When an equal number of students joined each school, the ratio of the students in Flynn School to that in Archie School became 4 : 3. How many students were there in both schools in the end?

	Archie School	Flynn School	Difference
Before	640		192
Change	+ ?	+ ?
After	4 u	3 u	1 u

Since an equal number of students joined 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 Archie School and Flynn School at first and in the end the same. 

Difference between the number of students in both schools at first
= 30% x 640
= ³⁰₁₀₀ x 640
= 192

Difference between the number of students in both schools in the end
= 4 u - 3 u
= 1 u

1 u = 192

Total number of students in both schools in the end
= 4 u + 3 u
= 7 u
= 7 x 192
= 1344

Answer(s): 1344