Concept: The question tests on the basics of Rounding.

Solution  :
 

A NEW OG 2021 QUESTION

As the side is exactly NOT 6,the area is exactly NOT 36 too and hence (A) can be eliminated.

Any number greater than or equal to 5.5 can be rounded off to 6.

=>The minimum side length to check for is 5.5.

(5.5)^2 = 30.25 is the minimum area with minimum side length of 5.5 (OPTION D)