Answer :
[tex]\bf \begin{array}{ccll}
\stackrel{cms}{map}&\stackrel{kms}{actual}\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
1&45\\
2&a
\end{array}\implies \cfrac{1}{2}=\cfrac{45}{a}\implies a=\cfrac{2\cdot 45}{1}[/tex]