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March 2nd, 2016, 05:10 PM   #1
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Algebra Word Problem

Can anyone help with my son's problem above?

Last edited by skipjack; March 2nd, 2016 at 05:30 PM.
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March 2nd, 2016, 05:56 PM   #2
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Originally Posted by scsims View Post
A box of 60 pens contains pens of four different colors. The box contains five times as many red pens as black pens, and four more black pens than green pens. The number of red, green, and black pens combined is three times the number of blue pens. How many pens of each color are in the box?
If there are n green pens, there are n+4 black pens and 5n+20 red pens,
so the number of blue pens is (n + n+4 + 5n+20)/3, i.e. 7n/3 + 8.

As the blue pens are outnumbered 3:1 by the others, there are 15 blue pens (and 45 others).

Hence 7n/3 + 8 = 15, and so n = 3.

There are therefore 3 green, 7 black, 35 red and 15 blue pens in the box.

Also answered here many years ago.
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