Find the lengths of the sides of a rectangle if its perimeter is 30 m and its width is 4 times shorter.

Let the width of the rectangle be x meters, then the length of the rectangle is 4 meters (if the length is 4 times shorter than the width, then the width, on the contrary, is 4 times longer than the length). By the condition of the problem, it is known that the perimeter of a rectangle (the perimeter of a rectangle is the sum of the lengths of its 4 sides; P = 2 (a + b)) is equal to 2 (x + 4x) meters or 30 meters. Let’s make an equation and solve it.

2 (x + 4x) = 30;

2 * 5x = 30;

10x = 30;

x = 30: 10;

x = 3 (m) – width;

4x = 3 * 4 = 12 (m) – length.

Answer. The length of the rectangle is 12 meters.