The perimeter of the rectangle is 36 cm and one of the sides is twice the other. What is the smallest of its sides?

Let’s denote:

P is the perimeter of the rectangle,

a – the length of the rectangle,

b is the width of the rectangle.

It is known from the problem statement that one of the sides is 2 times larger than the other. Let’s say a is the large side, b is the smaller side, then a = 2b.

The perimeter of a rectangle is equal to the sum of the lengths of all its sides:

P = a + b + a + b = 2a + 2b.

Let’s replace in this expression a = 2b:

P = 2 * 2b + 2b = 4b + 2b = 6b.

Since the size of the perimeter of the rectangle is known, you can calculate the length of the side b:

b = P: 6 = 36: 6 = 6 cm.

Answer: the length of the smaller side is 6 cm.