What is the ratio of the number of students appearing for the Aptitude Test from Town B to that from Town A?

Answer: Option B

Ratio of number of students from Town B to that from Town A
$$\begin{array}{rl}& =\frac{32.5\times 1000}{40\times 1000}\\ & =\frac{325}{400}\\ & =\frac{13}{16}\\ & =13:16\end{array}$$