In a bottle, the ratio of the number of pink marbles to the number of gold marbles was 1 : 4. Each time, 3 pink and 6 gold marbles were taken out of the bottle. A while later, only 144 gold marbles were left in the bottle. What was the total number of marbles in the bottle at first?

	Pink marbles	Gold marbles
Before	1x3 = 3 u	4x3 = 12 u
Change	- 3 u	- 6 u
After	0	144

Since there is no pink marbles left, this means that the number of pink marbles at first is the same as the number of pink marbles taken out.  

Make the number of pink marbles at first and taken out the same.  LCM of 1 and 3 is 3.

Number of gold marbles in the end
= 12 u - 6 u
= 6 u

6 u = 144

1 u = 144 ÷ 6 = 24

Total number of marbles in the bottle at first
= 3 u + 12 u
= 15 u
= 15 x 24
= 360

Answer: 360