The area of a rectangle, one side of which is 4cm, is equal to 36cm2. Find its perimeter.

To find the perimeter of a rectangle, let’s remember the formula:

P = 2 (a + b);

That is, in order to find the perimeter, we need to know the lengths of the two sides of the rectangle.

Let’s see what we know from the condition. We know that the length of one of the sides of the rectangle is 4 cm, and the area is 36 cm2.

In order to find the length of the second side of the rectangle, we will express it from the area formula.

S = a * b;

b = S / a;

Substitute and calculate:

b = 36/4 = 9 cm length of the second side of the rectangle.

We are looking for a perimeter:

P = 2 (a + b) = 2 (9 + 4) = 2 * 13 = 26 cm.