Carl School had 635 pupils and Mark School had 40% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Mark School to that in Carl School became 5 : 4. How many pupils were there in both schools in the end?

	Carl School	Mark School	Difference
Before	635		254
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 Carl School and Mark School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 40% x 635
= ⁴⁰₁₀₀ x 635
= 254

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

1 u = 254

Total number of pupils in both schools in the end
= 5 u + 4 u
= 9 u
= 9 x 254
= 2286

Answer(s): 2286