If the perimeter of a square is 20, what is the length of one side?

To find the length of one side of a square when the perimeter is given, it's essential to understand the relationship between the perimeter and the side length. The perimeter of a square is calculated by the formula:

[ \text{Perimeter} = 4 \times \text{side length} ]

Given that the perimeter is 20, you can set up the equation:

[ 20 = 4 \times \text{side length} ]

To find the length of one side, divide both sides of the equation by 4:

[ \text{side length} = \frac{20}{4} = 5 ]

Therefore, the length of one side of the square is 5.

This answer is correct because it follows the mathematical principles involved in calculating the perimeter and the properties of squares, where all four sides are of equal length.