Two identical squares were attached to each other with their sides so that a rectangle turned out.

Two identical squares were attached to each other with their sides so that a rectangle turned out. The perimeter of this rectangle is 42 cm. Find the perimeter of the square.

Because neither side of the rectangle is known, then an example is that the width of the rectangle is x, and the length will be 2x, because it is known that the rectangle consists of two squares. The perimeter is the sum of all sides of the rectangle:
P = (a + b) * 2.
Substitute the known values ​​and values ​​with variable x into the perimeter formula:
(x + 2x) * 2 = 42;
3x * 2 = 42;
6x = 42;
x = 42: 6;
x = 7 (cm) – the width of the rectangle;
7 * 2 = 14 (cm) – the length of the rectangle.
The width of the rectangle is the side of the square. To find the perimeter of a square, you need to multiply the side of the square by 4, because all sides of a square are equal:
4 * 7 = 28 (cm) – the perimeter of the square.