# Thread: help with fractions

1. ## help with fractions

if 5/n-1/2=3/36, what is the value of n?

posible answers: -2, 2, 9, 2/7

2. Originally Posted by lional
if 5/n-1/2=3/36, what is the value of n?

posible answers: -2, 2, 9, 2/7

we can start by reducing the fractions to get

$\displaystyle \frac{5}{n}-\frac{1}{2}=\frac{1}{12}$

The LCD of the equation is 12n so we multiply the whole equation by 12n to get

$\displaystyle \frac{60n}{n}-\frac{12n}{2}=\frac{12n}{12} \iff 60-6n=n$

$\displaystyle 60=7n \iff n=\frac{60}{7}$

This is not one of your choices but It is correct lets check and make sure.

So I will plug this into the original equation to get

$\displaystyle \frac{5}{\frac{60}{7}}-\frac{1}{2}\overbrace{=}^{?}\frac{1}{12}$

$\displaystyle \frac{35}{60}-\frac{1}{2}\overbrace{=}^{?}=\frac{1}{12}$

Getting a commond denominator I get

$\displaystyle \frac{35}{60}-\frac{30}{60}\overbrace{=}^{?}=\frac{1}{12}$

$\displaystyle \frac{5}{60}\overbrace{=}^{?}=\frac{1}{12}$

$\displaystyle \frac{1}{12}=\frac{1}{12}$

So the solution checks.

I hope this helps.