The perimeter of the rectangle is 40 dm. The length of its smaller side is 6 dm. How long is the longer side?

You can express the length of a rectangle from the formula to calculate its perimeter. Since the opposite sides of such a figure are equal, it corresponds to the formula:

P = 2a + 2b. By condition, the sum of all sides is 40 dm, width = 6 dm.

Let’s write the equation, substituting the known values:

2a + 2 * 6 = 40.

Variables are always shown on the left, and known values on the right. When transferring, the sign in front of them is reversed.

2a = 40 – 12 = 28.

To find the second factor, divide the product by the first:

a = 28: 2 = 14 dm.