There were some green pens and silver pens. The pens were packed into 2 bags. At first, Bag P contained 210 pens and 30% of them were silver pens. Bag Q contained 190 pens and 80% of them were silver pens. How many green pens and silver pens in total must be moved from Bag P to Bag Q such that 20% of the pens in Bag P are green and 50% of the pens in Bag Q are silver?

	Bag P		Bag Q
Total	210		190
	Silver pens	Green pens	Silver pens	Green pens
Before	63	147	152	38
Change	- ?	- ?	+ ?	+ ?
After	4 u	1 u	1 p	1 p

Number of silver pens in Bag P at first
= 30% x 210
= ³⁰₁₀₀ x 210
= 63

Number of green pens in Bag P at first
= 210 - 63
= 147

Number of silver pens in Bag Q at first
= 80% x 190
= ⁸⁰₁₀₀ x 190
= 152

Number of green pens in Bag Q at first
= 190 - 152
= 38

Bag P in the end
20% = ²⁰₁₀₀ =¹₅
Silver pens : Green pens = 4 : 1

Bag Q in the end
50% = ⁵⁰₁₀₀ =¹₂
Silver pens : Green pens = 1 : 1

Total number of silver pens = 4 u + 1 p

4 u + 1 p = 63 + 152
4 u + 1 p = 215 

1 p = 215 - 4 u --- (1)

Total number of green pens = 1 u + 1 p
1 u + 1 p = 147 + 38
1 u + 1 p = 185

1 p = 185 - 1 u --- (2)

(2) = (1)
185 - 1 u = 215 - 4 u
4 u - 1 u = 215 - 185
3 u = 30

1 u = 30 ÷ 3 = 10

Total number of green pens and silver pens that must be moved from Bag P to Bag Q
= 210 - 5 u
= 210 - 5 x 10
= 210 - 50
= 160

Answer(s): 160