Tom School had 605 pupils and Ken School had 20% more pupils. When an equal number of pupils left each school, the ratio of the pupils in Ken School to that in Tom School became 4 : 3. How many pupils were there in both schools in the end?

	Tom School	Ken School	Difference
Before	605		121
Change	- ?	- ?
After	4 u	3 u	1 u

Since an equal number of pupils left 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 Tom School and Ken School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 20% x 605
= ²⁰₁₀₀ x 605
= 121

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

1 u = 121

Total number of pupils in both schools in the end
= 4 u + 3 u
= 7 u
= 7 x 121
= 847

Answer(s): 847