Mark School had 755 pupils and Carl School had 40% less pupils. When an equal number of pupils joined each school, the ratio of the pupils in Carl School to that in Mark School became 4 : 3. How many pupils were there in both schools in the end?

	Mark School	Carl School	Difference
Before	755		302
Change	+ ?	+ ?
After	4 u	3 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 Mark School and Carl School at first and in the end the same. 

Difference between the number of pupils in both schools at first
= 40% x 755
= ⁴⁰₁₀₀ x 755
= 302

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

1 u = 302

Total number of pupils in both schools in the end
= 4 u + 3 u
= 7 u
= 7 x 302
= 2114

Answer(s): 2114