Ratio/Proportion: Given: A/B=7/9 and C/D=5/3; If B=4D, compute A+B/C+D

lei

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The problem is "Given: A/B=7/9 and C/D=5/3; If B=4D, compute A+B/C+D". It's not homework, just a practice problem, so no rush (not that there would be anyway, but you know). I don't really understand how to start. I've tried a lot of things, basically just creating equations and substituted, but nothing has worked. I'd appreciate if someone could show me how to begin finding the variables. Thanks!
 
… Given: A/B=7/9 and C/D=5/3; If B=4D, compute (A+B)/(C+D)

… I've tried a lot of things, basically just creating equations and substituted, but nothing has worked.
Those grouping symbols are very important; please ask, if you don't understand why.

You were probably on the right track, with some of your starts; maybe you didn't go far enough, before starting over. You didn't show any work, so I'm not sure what you tried.

Setting the cross-products equal to one another might be a good start.

9A = 7B

3C = 5D

Replace that B with 4D, and simplify: 9A = ?D

Expressions 9A and ?D represent the same number. We can divide each side of the equation 3C=5D by that number.

There are other ways to begin; I showed one example.

Next time you post, please show us your steps. Thank you. :cool:
 
Thanks!

Those grouping symbols are very important; please ask, if you don't understand why.

You were probably on the right track, with some of your starts; maybe you didn't go far enough, before starting over. You didn't show any work, so I'm not sure what you tried.

Setting the cross-products equal to one another might be a good start.

9A = 7B

3C = 5D

Replace that B with 4D, and simplify: 9A = ?D

Expressions 9A and ?D represent the same number. We can divide each side of the equation 3C=5D by that number.

There are other ways to begin; I showed one example.

Next time you post, please show us your steps. Thank you. :cool:

Thank you so much, I got the answer, I just hadn't gone far enough like you said
 
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