# Math Help - Double Stacked Fraction

1. ## Double Stacked Fraction

Okay, so here's my next drama:

It says the answer is: '√10a / 10'

However, how I am solving it is either multiplying either side by 2, then multiplying both sides again by the root 40 to rationalize the denominator.
The other way, dividing a/1 ÷ √40/2, then rationalizing, which gives me same wrong answer.
I've tried searching for ways to solve this type of question, but can't find anything. So please, how do I do this correctly?

2. ## Re: Double Stacked Fraction

in general

$\dfrac 1 {\dfrac a b}=\dfrac b a$

applied here we get

$\dfrac a {\dfrac{\sqrt{40}} 2}=a \cdot \dfrac 2 {\sqrt{40}}=\dfrac{2a}{\sqrt{4\cdot 10}}=\dfrac{2a}{2\sqrt{10}} =\dfrac a {\sqrt{10}}=\dfrac a {\sqrt{10}}\dfrac{\sqrt{10}}{\sqrt{10}}=\dfrac {\sqrt{10}a}{10}$

3. ## Re: Double Stacked Fraction

Ohh, ffs. I forgot about simplifying the root. That's where I went wrong. Thanks