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I have a bag with red and blue marbles in it. At the moment, the ratio of blue marbles to red marbles is 5:4. I then add 4 blue marbles and 4 red marbles, and the ratio becomes 6:5. How many blue marbles were in the bag before I added more?

 Aug 18, 2018
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B/R = 5/4.............................(1)
(B + 4)/(R + 4) = 6/5............(2)

From (1) above:
4B = 5R
B = 5R/4  sub this into (2) above

(5R/4 + 4)/(R + 4) =6/5, solve for R
R = 16 - original number of red marbles            
B = 20 - original number of blue marbles.

 Aug 18, 2018
edited by Guest  Aug 18, 2018

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