Zeph School had 535 pupils and Billy School had 40% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Billy School to that in Zeph School became 4 : 3. How many pupils were there in both schools in the end?

	Zeph School	Billy School	Difference
Before	535		214
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 Zeph School and Billy School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 40% x 535
= ⁴⁰₁₀₀ x 535
= 214

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

1 u = 214

Total number of pupils in both schools in the end
= 4 u + 3 u
= 7 u
= 7 x 214
= 1498

Answer(s): 1498