Ian School had 605 pupils and Luis School had 40% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Luis School to that in Ian School became 5 : 4. How many pupils were there in both schools in the end?

	Ian School	Luis School	Difference
Before	605		242
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 Ian School and Luis School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 40% x 605
= ⁴⁰₁₀₀ x 605
= 242

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

1 u = 242

Total number of pupils in both schools in the end
= 5 u + 4 u
= 9 u
= 9 x 242
= 2178

Answer(s): 2178