Math help?

Question

The lateral area of a cube is 256 square kilometers. What is its side length? 

4 kilometers 

8 kilometers 

24 kilometers 

22 kilometers

Answer 1

The lateral area of a cube is 4a²

But given lateral area of a cube is 256 square kilometers

                                      4a² = 256

                                        a² = 64

                                       a = 8 kilometers

So the side length of a cube is 8 kilometers

Option 2 is correct.