Answer: 1:4
It doesn't matter what the original side lengths were. If both dimensions are divided by 2, (halved) the Area of the new square will be 1/4 the Area of the original square.
Explanation:
But to prove it: 27×27 = 729 .
27/2 = 13.5 . 13.5 × 13.5 = 182.25
729/182.25 = 4 .or 182.25/729 = 0.25