There were some pink coins and yellow coins. The coins were packed into 2 bags. At first, Box S contained 300 coins and 30% of them were yellow coins. Box T contained 240 coins and 80% of them were yellow coins. How many pink coins and yellow coins in total must be moved from Box S to Box T such that 20% of the coins in Box S are pink and 50% of the coins in Box T are yellow?

	Box S		Box T
Total	300		240
	Yellow coins	Pink coins	Yellow coins	Pink coins
Before	90	210	192	48
Change	- ?	- ?	+ ?	+ ?
After	4 u	1 u	1 p	1 p

Number of yellow coins in Box S at first
= 30% x 300
= ³⁰₁₀₀ x 300
= 90

Number of pink coins in Box S at first
= 300 - 90
= 210

Number of yellow coins in Box T at first
= 80% x 240
= ⁸⁰₁₀₀ x 240
= 192

Number of pink coins in Box T at first
= 240 - 192
= 48

Box S in the end
20% = ²⁰₁₀₀ =¹₅
Yellow coins : Pink coins = 4 : 1

Box T in the end
50% = ⁵⁰₁₀₀ =¹₂
Yellow coins : Pink coins = 1 : 1

Total number of yellow coins = 4 u + 1 p

4 u + 1 p = 90 + 192
4 u + 1 p = 282 

1 p = 282 - 4 u --- (1)

Total number of pink coins = 1 u + 1 p
1 u + 1 p = 210 + 48
1 u + 1 p = 258

1 p = 258 - 1 u --- (2)

(2) = (1)
258 - 1 u = 282 - 4 u
4 u - 1 u = 282 - 258
3 u = 24

1 u = 24 ÷ 3 = 8

Total number of pink coins and yellow coins that must be moved from Box S to Box T
= 300 - 5 u
= 300 - 5 x 8
= 300 - 40
= 260

Answer(s): 260