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 ?

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