In a bag, there are red, yellow and blue marbles. There were twice as many red marbles as yellow marbles and twice as many yellow marbles as blue marbles at first. After removing 15 blue marbles and some yellow marbles from the bag, the number of red marbles became thrice that of the yellow marbles but the number of yellow marbles was still twice that of the blue marbles. What was the total number of marbles in the bag at first?
R Y B R Y B
-------------- ---------------
2 : 1 3 : 1
2 : 1 2 : 1
-------------- ---------------
4 : 2 : 1 6 : 2 : 1
-------------- ---------------
R Y B B B
-------------- x 2 x 6
4 : 2 : 1 2 6
- ? - 15 - 30 - 90
-------------- ----------------
6 : 2 : 1 2 6
-------------- -----------------
6 u – 90 -- > 4 u
2 u -- > 90
1 u -- > 90 ÷ 2 = 45
7 u -- > 7 x 45 = 315 marbles
The total number of marbles was 315 at first.
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