If 5.5 of a = 0.65 of b, then a : b is equal to = ?

Answer: Option C

$$\begin{array}{rl}& 5.5\text{a}=0.65\text{b}\\ & \Rightarrow \frac{55}{10}\text{a}=\frac{65}{100}\text{b}\\ & \Rightarrow 55\text{a}=\frac{65}{10}\text{b}\\ & \Rightarrow 550\text{a}=65\text{b}\\ & \text{a}:\text{b}=65:550\\ & =13:110\end{array}$$