Finding the perimeter of a parallelogram: formula and tasks

In this publication, we will consider how to calculate the perimeter of a parallelogram and analyze examples of solving problems.

Content

Perimeter Formula

The perimeter (P) of a parallelogram is equal to the sum of the lengths of all its sides. And since opposite sides of this figure are equal, the formula can be represented as follows:

P = 2 * (a + b) or P = 2a + 2b

Finding the perimeter of a parallelogram: formula and tasks

 

Examples of tasks

Task 1

Find the perimeter of a parallelogram if its sides are 6 and 8 cm.

Decision:

Let’s use one of the two formulas above, substituting the known values ​​into it: P u2d 6 * 2 cm + 8 * 28 cm uXNUMXd XNUMX cm.

The same result will be obtained if we apply the second formula: P u2d 6 * (8 cm + 28 cm) uXNUMXd XNUMX cm.

Task 2

The perimeter of the parallelogram is 50 cm. Find its second side if it is known that the first is 7 cm.

Decision:

We know that the perimeter is calculated by the formula: P = 2a + 2b.

Let’s say a is a known side, and we need to find b. Its length, multiplied by two, is equal to: 2b = P – 2a = 50 cm – 2 * 7 cm = 36 cm.

Therefore, the length of the unknown side is: b = 36 cm / 2 = 18 cm.

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