Howard, Mark and Cooper collected erasers in the ratio of 11 : 6 : 9. After Cooper gave ⁷₁₀ to Howard and Mark, Cooper had 404 less erasers than Howard. The number of erasers that Mark had increased by 75%. How many erasers did Howard and Cooper have in the end?

	Howard	Mark	Cooper
Before	11 u	6 u	9 u
Change	+ 1.8 u	+ 4.5 u	- 6.3 u
After	12.8 u	10.5 u	2.7 u

Number of erasers that Cooper gave to Howard and Mark
= ⁷₁₀ x 9 u
= 6.3 u

Number of erasers that Mark received from Cooper
= ⁷⁵₁₀₀ x 6 u
= 4.5 u

Number of erasers that Howard received from Cooper
= 6.3 u - 4.5 u
= 1.8 u

Number of less erasers that Cooper had less than Howard
= 12.8 u - 2.7 u 
= 10.1 u

10.1 u = 404

1 u = 404 ÷ 10.1 = 40

Number of erasers that Howard and Cooper had
= 12.8 u + 2.7 u
= 15.5 u
= 15.5 x 40
= 620

Answer(s): 620