Ethan, Japheth and Chen collected erasers in the ratio of 7 : 8 : 10. After Chen gave ³₄ to Ethan and Japheth, Chen had 312 less erasers than Ethan. The number of erasers that Japheth had increased by 20%. How many erasers did Ethan and Chen have in the end?

	Ethan	Japheth	Chen
Before	7 u	8 u	10 u
Change	+ 5.9 u	+ 1.6 u	- 7.5 u
After	12.9 u	9.6 u	2.5 u

Number of erasers that Chen gave to Ethan and Japheth
= ³₄ x 10 u
= 7.5 u

Number of erasers that Japheth received from Chen
= ²⁰₁₀₀ x 8 u
= 1.6 u

Number of erasers that Ethan received from Chen
= 7.5 u - 1.6 u
= 5.9 u

Number of less erasers that Chen had less than Ethan
= 12.9 u - 2.5 u 
= 10.4 u

10.4 u = 312

1 u = 312 ÷ 10.4 = 30

Number of erasers that Ethan and Chen had
= 12.9 u + 2.5 u
= 15.4 u
= 15.4 x 30
= 462

Answer(s): 462