George School had 310 pupils and Rael School had 30% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Rael School to that in George School became 4 : 3. How many pupils were there in both schools in the end?

	George School	Rael School	Difference
Before	310		93
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 George School and Rael School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 30% x 310
= ³⁰₁₀₀ x 310
= 93

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

1 u = 93

Total number of pupils in both schools in the end
= 4 u + 3 u
= 7 u
= 7 x 93
= 651

Answer(s): 651