The area of a rectangle is 300 dm2, its length is 20 dm larger. Find the perimeter of this rectangle.

Let the width of the rectangle be X dm, then, by condition, its length is (X + 20) dm.

The area of the rectangle is: S = 300 = X * (X + 20).

X ^ 2 + 20 * X – 300 = 0.

Let’s solve the quadratic equation.

X1 = -30. (Doesn’t fit because <0).

X2 = 10 cm.

Then the length is 10 + 20 = 30 cm.

Let’s define the perimeter of the rectangle:

P = 2 * (10 + 30) = 80 cm.

Answer: The perimeter of the rectangle is 80 cm.