Container Q contains 7 purple balls and 6 silver balls. Container R contains 132 purple balls and 65 silver balls. How many silver balls and purple balls must be transferred from Container R to put into Container Q so that 50% of the balls in Container A are purple and 70% of the balls in Container R are purple?

	Container Q		Container R
	Purple balls	Silver balls	Purple balls	Silver balls
Before	7	6	132	65
Change	+ ?	+ ?	- ?	- ?
After	1 u	1 u	7 p	3 p

50% = ⁵⁰₁₀₀ = 12

70% = ⁷⁰₁₀₀ = 710

Number of purple balls = 7 + 132 = 139 

Number of silver balls = 6 + 65 = 71 

1 u + 7 p = 139 --- (1)

1 u + 3 p = 71 ---(2)

(1) - (2)
(1 u + 7 p) - (1 u + 3 p) = 139 - 71
7 p - 3 p = 68
4 p = 68

1 p = 68 ÷ 4 = 17

From (2):
1 u + 3 p = 71
1 u + 3 x 17 = 71
1 u + 51 = 71

1 u = 71 - 51 = 20

Number of silver balls to be transferred from Container R to Container Q
= 65 - 3 p
= 65 - 3 x 17
= 65 - 51
= 14

Number of purple balls to be transferred from Container R to Container Q
= 1 u - 7
= 20 - 7
= 13

Total number of silver and purple balls to be transferred from Container R to Container Q
= 14 + 13
= 27

Answer(s): 27