In a bottle, the ratio of the number of pink marbles to the number of silver marbles was 1 : 3. Each time, 4 pink and 7 silver marbles were taken out of the bottle. A while later, only 150 silver marbles were left in the bottle. What was the total number of marbles in the bottle at first?

	Pink marbles	Silver marbles
Before	1x4 = 4 u	3x4 = 12 u
Change	- 4 u	- 7 u
After	0	150

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 4 is 4.

Number of silver marbles in the end
= 12 u - 7 u
= 5 u

5 u = 150

1 u = 150 ÷ 5 = 30

Total number of marbles in the bottle at first
= 4 u + 12 u
= 16 u
= 16 x 30
= 480

Answer: 480