In a proportion the product of 1st and 4th terms is 40 and that of 2nd and 3rd terms is 2.5x. Then the value of x is.

Answer: Option A

Product of 1^st and 4^th terms (extremes) = product of 2^nd and 3^rd terms (means)
$$\begin{array}{rl}& \Rightarrow \text{2}\text{.5}x=\text{40}\\ & \Rightarrow x=\frac{40}{2.5}=16\end{array}$$