Perimeter of the rectangle = 40 dm. Find the area of a rectangle if its length is 3 times its width.

We will solve this problem by writing an equation;

Let x dm be the width of the given rectangle;

Then 3 * x dm is the value of the length of this rectangle;

We also know that the value of the perimeter of this rectangle is 40 dm, we draw up an equation of the following form:

(x + 3 * x) * 2 = 40;

x + 3 * x = 20;

4 * x = 20;

x = 20: 4;

x = 5.

5 dm is the value of the width of this rectangle;

5 * 3 = 15 dm – this is the value of the length of this rectangle;

Let’s find the value of the area of ​​this rectangle, for this we need to multiply the value of the width of this rectangle by the value of the length of this rectangle:

5 * 15 = 75 dm2 is the value of the area of ​​this rectangle.

Answer: 75 dm2 is the value of the area of ​​this rectangle.