One side of the rectangle is 4 cm. Its perimeter is 28 cm. How long is the other side of the rectangle?

To solve this problem, remember that 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. Knowing that one side is 4 centimeters and the perimeter is 28 centimeters, we calculate the length of the second side.
2 * (4 + x) = 28;
8 + 2x = 28;
2x = 28 – 8;
2x = 20;
x = 20/2;
x = 10 cm.
Answer: 10 centimeters.