The length of the rectangle is 20cm and the width is 5cm less. Find the perimeter of the rectangle.

The perimeter of a rectangle is determined by the formula:

P = 2a + 2b.

Let us determine the sum of all sides of such a figure, the length of which is 20 cm, and the width is 5 cm less, by writing the expression:

P = 2 * 20 + 2 * (20 – 5). First of all, we find the values in brackets, then multiplication and division, and only then addition and subtraction, we perform all actions in order – from left to right:

P = 40 + 2 * 15 = 40 + 30 = 70 cm.