Albert School had 420 students and Ahmad School had 20% more students. When an equal number of students left each school, the ratio of the students in Ahmad School to that in Albert School became 4 : 3. How many students were there in both schools in the end?

	Albert School	Ahmad School	Difference
Before	420		84
Change	- ?	- ?
After	4 u	3 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 Albert School and Ahmad School at first and in the end the same. 

Difference between the number of students in both schools at first
= 20% x 420
= ²⁰₁₀₀ x 420
= 84

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

1 u = 84

Total number of students in both schools in the end
= 4 u + 3 u
= 7 u
= 7 x 84
= 588

Answer(s): 588