Three containers, A, B and C, contained 180 marbles. Warren added some marbles into Container A and the number of marbles in Container A tripled. He took out half of the number of marbles from Container B and removed 30 marbles from Container C. As a result, the ratio of the number of marbles in Container A, Container B and Container C became 12 : 3 : 5. What was the ratio of the number of marbles in Container C to the total number of marbles in Container A and Container B at first? Give the answer in its lowest term.

	Container A	Container B	Container C	Total
Before	1x4 = 4 u	2x3 = 6 u	5 u + 30	180
Change	+ 2x4 = + 8 u	- 1x3 = - 3 u	- 30
After	3x4 = 12 u	1x3 = 3 u
Comparing the 3 containers	12 u	3 u	5 u

The number of marbles in Container A in the end is the same. Make the number of marbles in Container A in the end the same. LCM of 3 and 12 is 12.

The number of marbles in Container B in the end is the same. Make the number of marbles in Container B in the end the same. LCM of 1 and 3 is 3.

Total number of marbles at first
= 4 u + 6 u + 5 u + 30
= 15 u + 30

15 u + 30 = 180
15 u = 180 - 30
15 u = 150

1 u = 150 ÷ 15 = 10

Number of marbles in Container C at first
= 5 u + 30
= 5 x 10 + 30
= 50 + 30
= 80

Number of marbles in Container A and Container B at first
= 180 - 80
= 100

Container C : Container A and Container B
80 : 100 _(÷20)
4 : 5

Answer(s): 4 : 5