(23)/(120x) = 1/5. Solve for X

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  • #1
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How is it done?

Having to solve for X when X is in the denominator really confuses me. Please help!
 

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  • #2
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How is it done?

Having to solve for X when X is in the denominator really confuses me. Please help!
Just multiply both sides by 120*x and remember that this works as long as 120*x =/= 0 which means
that x=/=0 in your final solution because dividing by zero is not defined.
 
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  • #3
Mentallic
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Remember that

[tex]a\cdot\frac{b}{c} = \frac{a}{c}\cdot b =\frac{ab}{c}[/tex]

(The dot means multiply) so if we multiply

[tex]\frac{23}{120x}=\frac{1}{5}[/tex]

by the denominator in the left fraction (which is 120x) then we get

[tex]120x\cdot\frac{23}{120x}=120x\cdot\frac{1}{5}[/tex]

And now we can cancel 120x from the left side because

[tex]120x\cdot\frac{23}{120x} = \frac{120x}{120x}\cdot 23 = 1\cdot 23=23[/tex]

So we now have

[tex]23=\frac{120x}{5}[/tex]

Now you can solve the rest in the usual way you've been solving equations.
Also, keep in mind that you can have just multiplied through by x rather than 120x.
 
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  • #4
Student100
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This problem looks like it was made for cross multiplication, is that what they're teaching you right now?
 
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  • #5
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As an alternative, if two fractions are equal, then their reciprocals are equal.

IOW, if a/b = c/d, then b/a = d/c, barring of course the possibility that any of the numbers are zero.

In the context of this problem, you can rewrite 23/(120x) = 1/5 as 120x/23 = 5.
 

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