There were some pink pens and white pens. The pens were packed into 2 bags. At first, Packet N contained 240 pens and 30% of them were white pens. Packet P contained 180 pens and 80% of them were white pens. How many pink pens and white pens in total must be moved from Packet N to Packet P such that 30% of the pens in Packet N are pink and 50% of the pens in Packet P are white?

	Packet N		Packet P
Total	240		180
	White pens	Pink pens	White pens	Pink pens
Before	72	168	144	36
Change	- ?	- ?	+ ?	+ ?
After	7 u	3 u	1 p	1 p

Number of white pens in Packet N at first
= 30% x 240
= ³⁰₁₀₀ x 240
= 72

Number of pink pens in Packet N at first
= 240 - 72
= 168

Number of white pens in Packet P at first
= 80% x 180
= ⁸⁰₁₀₀ x 180
= 144

Number of pink pens in Packet P at first
= 180 - 144
= 36

Packet N in the end
30% = ³⁰₁₀₀ =³₁₀
White pens : Pink pens = 7 : 3

Packet P in the end
50% = ⁵⁰₁₀₀ =¹₂
White pens : Pink pens = 1 : 1

Total number of white pens = 7 u + 1 p

7 u + 1 p = 72 + 144
7 u + 1 p = 216 

1 p = 216 - 7 u --- (1)

Total number of pink pens = 3 u + 1 p
3 u + 1 p = 168 + 36
3 u + 1 p = 204

1 p = 204 - 3 u --- (2)

(2) = (1)
204 - 3 u = 216 - 7 u
7 u - 3 u = 216 - 204
4 u = 12

1 u = 12 ÷ 4 = 3

Total number of pink pens and white pens that must be moved from Packet N to Packet P
= 240 - 10 u
= 240 - 10 x 3
= 240 - 30
= 210

Answer(s): 210