SOLUTION: A bag contains 7 red marbles and 5 black marbles. You want to add 60 marbles to the bag, but the ratio of red to black marbles must remain the same. How many of each color should y

Algebra ->  Probability-and-statistics -> SOLUTION: A bag contains 7 red marbles and 5 black marbles. You want to add 60 marbles to the bag, but the ratio of red to black marbles must remain the same. How many of each color should y      Log On


   

Question 584625: A bag contains 7 red marbles and 5 black marbles. You want to add 60 marbles to the bag, but the ratio of red to black marbles must remain the same. How many of each color should you add?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A bag contains 7 red marbles and 5 black marbles. You want to add 60 marbles to the bag, but the ratio of red to black marbles must remain the same. How many of each color should you add?
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b + r = 60
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(7+r)/(5+b) = 7/5
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35+5r = 35 + 7b
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5r = 7b
Substitute for "r"
5(60-b) = 300-5b = 7b
12b = 300
b = 25 # of the 60 that should be black)
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Solve for "r":
r = 60-b
r = 60-25
r = 35 (# of the 60 that should be red)
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Cheers,
Stan H.