Ivan School had 700 pupils and Fabian School had 25% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Fabian School to that in Ivan School became 5 : 4. How many pupils were there in both schools in the end?

	Ivan School	Fabian School	Difference
Before	700		175
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 Ivan School and Fabian School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 25% x 700
= ²⁵₁₀₀ x 700
= 175

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

1 u = 175

Total number of pupils in both schools in the end
= 5 u + 4 u
= 9 u
= 9 x 175
= 1575

Answer(s): 1575