A snapshot 17/8 × 21/2 is to be enlarged so that the longer dimension is 4. What will be the dimension of the shorter side ?

Answer: Option C

Let the dimension of the shorter side be x
More is the longer side, More is the shorter side (Direct proportion)
$$\begin{array}{rl}& \therefore 2\frac{1}{2}:4::1\frac{7}{8}:x\\ & \iff \frac{5}{2}x=4\times \frac{15}{8}\\ & \iff x=\left(\frac{15}{2}\times \frac{2}{5}\right)\\ & \iff x=3\end{array}$$