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#1 2005-07-10 05:26:37

anonymous
Guest

proportions

3/(5x+1)=2/9, x=?

#2 2005-07-10 06:36:25

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: proportions

3/(5x+1)=2/9
Multiply by (5x+1): 3=2(5x+1)/9
Multiply by 9: 27=2(5x+1)
Multiply out of brackets: 27=10x+2
Take away 2: 25=10x
Divide by 10: x=2.5

Hope this helps!


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It wanted to be normal.

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#3 2005-07-10 16:47:34

ganesh
Moderator
Registered: 2005-06-28
Posts: 14,410

Re: proportions

This can be explained in another way.
when you have a/b=c/d,
you get ad=bc.
In this problem,
3/(5x+1) = 2/9,
therefore, 9x3 = 2(5x+1)
27=10x+2
Move 2 to the other side, by changing the sign,
27-2 = 10x,
25=10x,
x = 25/10 = 2.5


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