The width of the rectangle is half its length. Calculate the sum of the sides of a rectangle if its width is 5 cm.

The perimeter of a rectangle is the sum of the lengths of all its sides. Since in a rectangle the opposite sides are equal, then P = 2 * (a + b), where a is the length, b is the width. We calculate the length, knowing that the width is 5 cm.
5 * 2 = 10 cm.
Let’s calculate the sum of the sides of the rectangle.
P = 2 * (10 + 5) = 2 * 15 = 30 cm.
Answer: 30 cm.