Given:
Area of a square wall tile ; 58,800 mm²
To get an area of square simply multiply its side length by itself or raise it to the 2nd power.
Area = a² ; a = side length.
58,800 mm² = a²
√58,800 mm² = √a²
a = 242.487 or 242.49 mm
The length of one side is between 242mm and 243mm.