There were some yellow stickers and black stickers. The stickers were packed into 2 bags. At first, Packet N contained 190 stickers and 30% of them were black stickers. Packet P contained 470 stickers and 60% of them were black stickers. How many yellow stickers and black stickers in total must be moved from Packet N to Packet P such that 25% of the stickers in Packet N are yellow and 50% of the stickers in Packet P are black?

	Packet N		Packet P
Total	190		470
	Black stickers	Yellow stickers	Black stickers	Yellow stickers
Before	57	133	282	188
Change	- ?	- ?	+ ?	+ ?
After	3 u	1 u	1 p	1 p

Number of black stickers in Packet N at first
= 30% x 190
= ³⁰₁₀₀ x 190
= 57

Number of yellow stickers in Packet N at first
= 190 - 57
= 133

Number of black stickers in Packet P at first
= 60% x 470
= ⁶⁰₁₀₀ x 470
= 282

Number of yellow stickers in Packet P at first
= 470 - 282
= 188

Packet N in the end
25% = ²⁵₁₀₀ =¹₄
Black stickers : Yellow stickers = 3 : 1

Packet P in the end
50% = ⁵⁰₁₀₀ =¹₂
Black stickers : Yellow stickers = 1 : 1

Total number of black stickers = 3 u + 1 p

3 u + 1 p = 57 + 282
3 u + 1 p = 339 

1 p = 339 - 3 u --- (1)

Total number of yellow stickers = 1 u + 1 p
1 u + 1 p = 133 + 188
1 u + 1 p = 321

1 p = 321 - 1 u --- (2)

(2) = (1)
321 - 1 u = 339 - 3 u
3 u - 1 u = 339 - 321
2 u = 18

1 u = 18 ÷ 2 = 9

Total number of yellow stickers and black stickers that must be moved from Packet N to Packet P
= 190 - 4 u
= 190 - 4 x 9
= 190 - 36
= 154

Answer(s): 154