The perimeter of the rectangle 40 is equal to the area of this rectangle if its length is 3 times its width.

According to the condition of the task, we will compose an equation where we take the smallest side of the rectangle for x, the length for 3x, and the sum of all sides = 40 cm.

The perimeter is calculated using the formula:

P = 2a + 2b. Substitute the values and get:

2 * 3x + 2x = 40. Let’s perform actions with the coefficients of the variable on the left side of the equation:

8x = 40. To find the second factor, divide the product by the first:

x = 40: 8 = 5.

Therefore, width = 5 cm and length = 3 * 5 = 15 cm.

Let’s define the area of such a figure:

S = a * b = 15 * 5 = 75 cm².