1 / 4/5 + 1/v = 1/f

Find the value of v

1 / 4/5 + 1/v = 1 / 2/3 - 1 / 4/5 = 1/v

1 / 2/3 - 1 / 4/5 = 5/3 - 1 x 9 / 1 x 5 = 5/3 - 9/5 =

5 x 5 / 3 x 9 = 25 / 27

I am sure I am not quite right with this?

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- Nov 18th 2011, 03:19 AMDavid GreenFinding an unknown in a formula
1 / 4/5 + 1/v = 1/f

Find the value of v

1 / 4/5 + 1/v = 1 / 2/3 - 1 / 4/5 = 1/v

1 / 2/3 - 1 / 4/5 = 5/3 - 1 x 9 / 1 x 5 = 5/3 - 9/5 =

5 x 5 / 3 x 9 = 25 / 27

I am sure I am not quite right with this? - Nov 18th 2011, 03:44 AMemakarovRe: Finding an unknown in a formula
By 1 / 4/5 do you mean (a) $\displaystyle 1\tfrac{4}{5}$, (b) $\displaystyle \frac{1}{4/5}$ or (c) $\displaystyle \frac{1/4}{5}$? These options can be rendered in text as follows: (a) 1 4/5, (b) 1 / (4 / 5) and (c) (1 / 4) / 5 (maybe also adding a note would help).

Your equation has two variables: v and f, so at most you can express v through f.

LaTeX formulas have to be surrounded by [TEX]...[/TEX] tags (that's the rightmost button over the text area where you type your post, after you press "Preview Post" button). - Nov 18th 2011, 03:47 AMDavid GreenRe: Finding an unknown in a formula
- Nov 18th 2011, 04:18 AMemakarovRe: Finding an unknown in a formula
Since $\displaystyle \frac{1}{4/5}=\frac{5}{4}$, the equation is $\displaystyle \frac{5}{4}+\frac{1}{v}=\frac{1}{f}$.

$\displaystyle \frac{1}{v}=\frac{1}{f}-\frac{5}{4}=\frac{4-5f}{4f}$

$\displaystyle v=\frac{4f}{4-5f}$ - Nov 18th 2011, 04:50 AMDavid GreenRe: Finding an unknown in a formula