Answer: 2cm^2 by 2cm^2
Step-by-step explanation:
The area of the poster is 4cm by 4cm(all sides equal) which is 16cm^2.
If this is fixed at 384cm^2, the length of the 384cm^2 poster will be √384 which is 18cm^2.
Which means that a poster of side 4cm^2 us fixed inside poster with side 18cm^2.
To get the dimension with smallest area, we divide 18cm^2 by 4cm^2 and the remainder will be the smallest dimension i.e 2cm^2 by 2cm^2