Sean School had 630 students and Charlie School had 40% less students. When an equal number of students joined each school, the ratio of the students in Charlie School to that in Sean School became 5 : 4. How many students were there in both schools in the end?

	Sean School	Charlie School	Difference
Before	630		252
Change	+ ?	+ ?
After	5 u	4 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 Sean School and Charlie School at first and in the end the same. 

Difference between the number of students in both schools at first
= 40% x 630
= ⁴⁰₁₀₀ x 630
= 252

Difference between the number of students in both schools in the end
= 5 u - 4 u
= 1 u

1 u = 252

Total number of students in both schools in the end
= 5 u + 4 u
= 9 u
= 9 x 252
= 2268

Answer(s): 2268