Answer:
8
Explanation:
So a rectangle that would be 4 cm high and 16 cm long has an area of 64 square cm. A square is a rectangle where the height and width are the same value, so you need to find a number, when multiplied by itself, will give you 64… which is to say the square root of 64. And that's 8. 8 x 8 = 64.