SOLUTION: A bag contains 80 more red marbles than black marbles. If the ratio of red to black is 9 to 4, how many marbles are in the bag altogether?

Question 601747: A bag contains 80 more red marbles than black marbles. If the ratio of red to black is 9 to 4, how many marbles are in the bag altogether?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A bag contains 80 more red marbles than black marbles. If the ratio of red to black is 9 to 4, how many marbles are in the bag altogether?
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Let number of black be "x"
Then number of red = "x+80"
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Equation:
(x+80)/x = 9/4
Cross-multiply:
4x+320 = 9x
5x = 320
x = 64 (# of black)
x + 80 = 144 (# of red)
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Cheers,
Stan H.
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