ANSWER
4 : 5
EXPLANATION
We have the ratio 16 : 20 and we want to reduce it to lowest form.
This means that we have to factor out any number that is common between the two numbers in the ratio.
We have:
[tex]\begin{gathered} 16\text{ : 20 = }\frac{16}{20} \\ \text{Divide both numerator and denominator by 4:} \\ \Rightarrow\text{ }\frac{4}{5}\text{ = 4 : 5} \end{gathered}[/tex]The lowest form of the ratio is 4 : 5
