Dylan School had 720 pupils and Simon School had 30% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Simon School to that in Dylan School became 4 : 3. How many pupils were there in both schools in the end?

	Dylan School	Simon School	Difference
Before	720		216
Change	+ ?	+ ?
After	4 u	3 u	1 u

Since an equal number of pupils joined 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 Dylan School and Simon School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 30% x 720
= ³⁰₁₀₀ x 720
= 216

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

1 u = 216

Total number of pupils in both schools in the end
= 4 u + 3 u
= 7 u
= 7 x 216
= 1512

Answer(s): 1512