Xavier School had 480 pupils and Oscar School had 20% more pupils. When an equal number of pupils left each school, the ratio of the pupils in Oscar School to that in Xavier School became 4 : 3. How many pupils were there in both schools in the end?

	Xavier School	Oscar School	Difference
Before	480		96
Change	- ?	- ?
After	4 u	3 u	1 u

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

Difference between the number of pupils in both schools at first
= 20% x 480
= ²⁰₁₀₀ x 480
= 96

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

1 u = 96

Total number of pupils in both schools in the end
= 4 u + 3 u
= 7 u
= 7 x 96
= 672

Answer(s): 672