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Source: — Problem Solving |
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by palvarez » Mon Nov 16, 2009 1:36 am
(5k-10)/(3k+10)= 7/5, find 2k-20

25k-50 = 21k+70
4k = 120
2k = 60

2k-20 = 40
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by cbenk121 » Mon Nov 16, 2009 1:24 pm
palvarez wrote:(5k-10)/(3k+10)= 7/5, find 2k-20

25k-50 = 21k+70
4k = 120
2k = 60

2k-20 = 40
Can you explain a little more on how you set it up? I see how it's set up and get what it means, but want to see the thought process. I believe I was originally setting up something like (5x + 3x) = (7x-10) + (5x + 10), knowing the total number of stamps didn't change, but this simplfies down to 3x = 7x lol.

Then, how did you know it was 2x-20 you were looking for?
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Master | Next Rank: 500 Posts
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by palvarez » Mon Nov 16, 2009 1:26 pm
whenever you are given a ratio, you can translate it into equations

a/b = 5/3

a = 5k and b = 3k

remove 10 from a and add 10 to b, resulting ration is 7/5

(5k-10)/(3k+10) = 7/5

Whats the difference between new numerator n denominator = 5k- 10 -(3k+10) = 2k - 20
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