Hi everyone! I'm a little stuck on my ratio calculation.

Thanks Miss Melody :)

Thanks Lance :)

And thanks Heureka 

I think because it ask you to relate 1:4 to 5:a then it should be in 5:20 or 5/20 form.

Hi Eloise,

For starters you have too many equal signs.  I'll get rid of the excess ones.

1:4 =5:a

1/4=5/a

1/4=5/20       At this point you have the answer, a=20

Lets look at another way to do this :)

$$\\\frac{1}{4}=\frac{5}{a}\\\\
$Multiply both sides by $\frac{a}{1}\;\;$this is to get a off the bottom$\\\\
\frac{1}{4}\times \frac{a}{1} =\frac{5}{a}\times \frac{a}{1}\\\\
$simplify$\\\\
\frac{a}{4} =5\\\\
$Multiply both sides by 4 to get a by itself$\\\\
\frac{a}{4}\times 4 =5\times 4\\\\
$Simplify$\\\\
a=20$$

1:4 =5:a       a = ?

$$\\
\small{\text{$
\begin{array}{rclcrcl}
1\cdot \frac{4}{1} &=& 4 &\rm{~~or~~}& 1\cdot \mathbf{4} &=& 4\\\\
&& &\rm{~~so~~}&5\cdot \mathbf{4} &=& a\\\\
&&&&\textcolor[rgb]{1,0,0}{a}&\textcolor[rgb]{1,0,0}{=}& \textcolor[rgb]{1,0,0}{20}
\end{array}
$}}$$