There were some yellow erasers and silver erasers. The erasers were packed into 2 bags. At first, Bag W contained 290 erasers and 30% of them were silver erasers. Bag X contained 280 erasers and 75% of them were silver erasers. How many yellow erasers and silver erasers in total must be moved from Bag W to Bag X such that 25% of the erasers in Bag W are yellow and 50% of the erasers in Bag X are silver?

	Bag W		Bag X
Total	290		280
	Silver erasers	Yellow erasers	Silver erasers	Yellow erasers
Before	87	203	210	70
Change	- ?	- ?	+ ?	+ ?
After	3 u	1 u	1 p	1 p

Number of silver erasers in Bag W at first
= 30% x 290
= ³⁰₁₀₀ x 290
= 87

Number of yellow erasers in Bag W at first
= 290 - 87
= 203

Number of silver erasers in Bag X at first
= 75% x 280
= ⁷⁵₁₀₀ x 280
= 210

Number of yellow erasers in Bag X at first
= 280 - 210
= 70

Bag W in the end
25% = ²⁵₁₀₀ =¹₄
Silver erasers : Yellow erasers = 3 : 1

Bag X in the end
50% = ⁵⁰₁₀₀ =¹₂
Silver erasers : Yellow erasers = 1 : 1

Total number of silver erasers = 3 u + 1 p

3 u + 1 p = 87 + 210
3 u + 1 p = 297 

1 p = 297 - 3 u --- (1)

Total number of yellow erasers = 1 u + 1 p
1 u + 1 p = 203 + 70
1 u + 1 p = 273

1 p = 273 - 1 u --- (2)

(2) = (1)
273 - 1 u = 297 - 3 u
3 u - 1 u = 297 - 273
2 u = 24

1 u = 24 ÷ 2 = 12

Total number of yellow erasers and silver erasers that must be moved from Bag W to Bag X
= 290 - 4 u
= 290 - 4 x 12
= 290 - 48
= 242

Answer(s): 242