In a jar, the ratio of the number of silver marbles to the number of blue marbles was 1 : 4. Each time, 3 silver and 6 blue marbles were taken out of the jar. A while later, only 162 blue marbles were left in the jar. What was the total number of marbles in the jar at first?

	Silver marbles	Blue marbles
Before	1x3 = 3 u	4x3 = 12 u
Change	- 3 u	- 6 u
After	0	162

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

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

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

6 u = 162

1 u = 162 ÷ 6 = 27

Total number of marbles in the jar at first
= 3 u + 12 u
= 15 u
= 15 x 27
= 405

Answer: 405