SOLUTION: A bag has 3 parts green marbles and 5 parts blue marbles. If there are 72 total marbles in the bag, how many of them are blue?

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Question 721113: A bag has 3 parts green marbles and 5 parts blue marbles. If there are 72 total marbles in the bag, how many of them are blue?
Answer by fcabanski(1391) About Me  (Show Source):
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For the numbers the problem gives there are 5 blue marbles for every 5+3 = 8 marbles. The ratio is 5 to 8 or 5/8. That's blue/total.


For the unknown number the denominator (total) is 72 and blue is unknown, so call it x. The ratio is x to 72 or x/72.


Create a proportion by setting the ratios equal: 5/8 = x/72.


Cross multiply: 5*72 = 8x ---> 360=8x ---> (divide both sides by 8) 45=x.


There are 45 blue marbles and 27 green marbles in the bag.

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