Eric School had 580 pupils and Andy School had 40% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Andy School to that in Eric School became 5 : 4. How many pupils were there in both schools in the end?

	Eric School	Andy School	Difference
Before	580		232
Change	+ ?	+ ?
After	5 u	4 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 Eric School and Andy School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 40% x 580
= ⁴⁰₁₀₀ x 580
= 232

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

1 u = 232

Total number of pupils in both schools in the end
= 5 u + 4 u
= 9 u
= 9 x 232
= 2088

Answer(s): 2088