What will be the new area of blue square if the side of the square is reduced to one third of its current size? (one square box is one square unit)

Given:
Side of the blue square$=3 \mathrm{units}$

area of blue square $=9 \mathrm{square} \mathrm{units}$

To calculate:
New area of blue square, if its side is reduced to one third of its current size

Calculation:
If the side is reduced to one-third of its current size, the new side$=\frac{1}{3}\times 3=1 \mathrm{unit}$

$\Rightarrow$new area$=1\times 1=1 \mathrm{square} \mathrm{units}$

Hence, the correct answer is Option D.