The dimensions of a certain machine are 48" × 30" × 52". If the size of the machine is increased proportionately until the sum of its dimensions equal 156", what will be the increase in the shortest side ?

Answer: Option B

Sum of original dimension :
$$\begin{array}{rl}& =48+30+52\\ & =130\end{array}$$
Increase in sum :
$$\begin{array}{rl}& =156-130\\ & =26\end{array}$$
Since the dimensions have been increased proportionately,
So increase in shortest side :
$$=\left(26\times \frac{30}{130}\right)$$   "
$$=6$$ "