# Thread: Relatively basic fraction multplication!

1. ## Relatively basic fraction multplication!

Hi all,

The below expression is part of a longer equation which I have simplified for this example. I would like to remove the r from the very bottom denominator. What do I multiply the remaining variables by?

a/b * (1-cd)/(1-(cd/r)) + e/f

Many thanks in advance!

2. ## Re: Relatively basic fraction multplication!

$\displaystyle \frac{a}{b} \cdot \frac{1-cd}{1-\frac{cd}{r}} + \frac{e}{f}$

i assume that by "very bottom denominator" you mean the $\displaystyle \frac{cd}{r}$ part.

multiply everything by 1/r

$\displaystyle \frac{a}{b} \cdot \frac{1-cd}{r \left(1-\frac{cd}{r} \right)} + \frac{e}{fr}$

$\displaystyle = \frac{a}{b} \cdot \frac{1-cd}{r-cd} + \frac{e}{fr}$

Thanks!

4. ## Re: Relatively basic fraction multplication!

oh dear, how silly of me, if you wanted a fraction that was equivalent to he first one, that wont be it....as the above is multiplied by (1/r)

hopefully you made appropriate adjustments to ther est of your equation.

5. ## Re: Relatively basic fraction multplication!

Originally Posted by ktharmer
a/b * (1-cd)/(1-(cd/r)) + e/f
1 - cd/r = (r - cd) / r
So:
a/b * [r(1 - cd) / (r - cd)] + e/f