Rael, Charlie and Cooper collected erasers in the ratio of 9 : 6 : 4. After Cooper gave ¹₅ to Rael and Charlie, Cooper had 180 less erasers than Rael. The number of erasers that Charlie had increased by 10%. How many erasers did Rael and Cooper have in the end?

	Rael	Charlie	Cooper
Before	9 u	6 u	4 u
Change	+ 0.2 u	+ 0.6 u	- 0.8 u
After	9.2 u	6.6 u	3.2 u

Number of erasers that Cooper gave to Rael and Charlie
= ¹₅ x 4 u
= 0.8 u

Number of erasers that Charlie received from Cooper
= ¹⁰₁₀₀ x 6 u
= 0.6 u

Number of erasers that Rael received from Cooper
= 0.8 u - 0.6 u
= 0.2 u

Number of less erasers that Cooper had less than Rael
= 9.2 u - 3.2 u 
= 6 u

6 u = 180

1 u = 180 ÷ 6 = 30

Number of erasers that Rael and Cooper had
= 9.2 u + 3.2 u
= 12.4 u
= 12.4 x 30
= 372

Answer(s): 372