document.write( "Question 810229: A bag contains 7 red marbles and 5 black marbles. You must add 60 marbles to the bag, but the ratio of red to black must remain the same. How many of each color should you add? \n" ); document.write( "

Algebra.Com's Answer #488046 by DrBeeee(684) $\"\"$ $\"About$

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You have 7 red marbles and 5 black marbles for a total number of 12 marbles, right? When you add 60, you have a new total of 72, correct? To keep the same ratio of red/total, we have the proportion
\n" ); document.write( "(1) 7/12 = red/72 or
\n" ); document.write( "(2) red = 72*7/12 or
\n" ); document.write( "(3) red = 42
\n" ); document.write( "That is, you will have 42 total red marble and
\n" ); document.write( "(4) black = 72 - 42 = 30 or we have a total of 30 black marbles
\n" ); document.write( "The ratio of red to black is
\n" ); document.write( "(6) 42/30 = 7/5, the same as before we added 60 marbles.
\n" ); document.write( "Answer: We should add 35 red marbles and 25 black marbles (total of 60 marbles). \n" ); document.write( "

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