There were some brown stamps and yellow stamps. The stamps were packed into 2 bags. At first, Packet S contained 210 stamps and 30% of them were yellow stamps. Packet T contained 490 stamps and 60% of them were yellow stamps. How many brown stamps and yellow stamps in total must be moved from Packet S to Packet T such that 25% of the stamps in Packet S are brown and 50% of the stamps in Packet T are yellow?

	Packet S		Packet T
Total	210		490
	Yellow stamps	Brown stamps	Yellow stamps	Brown stamps
Before	63	147	294	196
Change	- ?	- ?	+ ?	+ ?
After	3 u	1 u	1 p	1 p

Number of yellow stamps in Packet S at first
= 30% x 210
= ³⁰₁₀₀ x 210
= 63

Number of brown stamps in Packet S at first
= 210 - 63
= 147

Number of yellow stamps in Packet T at first
= 60% x 490
= ⁶⁰₁₀₀ x 490
= 294

Number of brown stamps in Packet T at first
= 490 - 294
= 196

Packet S in the end
25% = ²⁵₁₀₀ =¹₄
Yellow stamps : Brown stamps = 3 : 1

Packet T in the end
50% = ⁵⁰₁₀₀ =¹₂
Yellow stamps : Brown stamps = 1 : 1

Total number of yellow stamps = 3 u + 1 p

3 u + 1 p = 63 + 294
3 u + 1 p = 357 

1 p = 357 - 3 u --- (1)

Total number of brown stamps = 1 u + 1 p
1 u + 1 p = 147 + 196
1 u + 1 p = 343

1 p = 343 - 1 u --- (2)

(2) = (1)
343 - 1 u = 357 - 3 u
3 u - 1 u = 357 - 343
2 u = 14

1 u = 14 ÷ 2 = 7

Total number of brown stamps and yellow stamps that must be moved from Packet S to Packet T
= 210 - 4 u
= 210 - 4 x 7
= 210 - 28
= 182

Answer(s): 182