Container L contains 9 white marbles and 10 purple marbles. Container M contains 90 white marbles and 41 purple marbles. How many purple marbles and white marbles must be moved from Container M to put into Container L so that 50% of the marbles in Container A are white and 70% of the marbles in Container M are white?

	Container L		Container M
	White marbles	Purple marbles	White marbles	Purple marbles
Before	9	10	90	41
Change	+ ?	+ ?	- ?	- ?
After	1 u	1 u	7 p	3 p

50% = ⁵⁰₁₀₀ = 12

70% = ⁷⁰₁₀₀ = 710

Number of white marbles = 9 + 90 = 99 

Number of purple marbles = 10 + 41 = 51 

1 u + 7 p = 99 --- (1)

1 u + 3 p = 51 ---(2)

(1) - (2)
(1 u + 7 p) - (1 u + 3 p) = 99 - 51
7 p - 3 p = 48
4 p = 48

1 p = 48 ÷ 4 = 12

From (2):
1 u + 3 p = 51
1 u + 3 x 12 = 51
1 u + 36 = 51

1 u = 51 - 36 = 15

Number of purple marbles to be moved from Container M to Container L
= 41 - 3 p
= 41 - 3 x 12
= 41 - 36
= 5

Number of white marbles to be moved from Container M to Container L
= 1 u - 9
= 15 - 9
= 6

Total number of purple and white marbles to be moved from Container M to Container L
= 5 + 6
= 11

Answer(s): 11