Let’s learn how to determine the perimeter of a rectangle.
What is a Rectangle?
A rectangle is a four-sided flat shape with two pairs of parallel and congruent lines that form a right angle on each of the four sides. A rectangle is also called a parallelogram – a quadrilateral whose opposite sides are equal and parallel. By this definition, we can infer that a square is a rectangle, but a rectangle is not a square. Examples of a rectangle are mobile phones, chalkboard, and TV.
Related Reading: Area of a Rectangle – Formula & Examples
How to Find the Perimeter of a Rectangle:
Perimeter refers to the total length around a shape. To find the perimeter of a rectangle, add up the lengths of its four sides, as expressed in this formula:
P = 2L + 2W
where L = Length and W = Width
Here’s a quick guide to computing perimeters:
Step 1. Write down the given length and width. Make sure all measurement units are the same. If not, convert either of them to match the unit of the other.
Step 2. Plug the figures into the formula: P = 2L + 2W.
Step 3. Perform the operations: multiplication then addition. Don’t forget to write the measurement unit together with the answer.
Example 1: Finding the Perimeter when given Length and Width of a Rectangle
Find the perimeter of the rectangle below.
Solution to Example 1:
Start by writing down the given figures, the length (L = 10cm) and width (W = 8cm).
Substitute 10cm for L and 8cm for W in the formula.
P = 2L + 2W
P = 2(10cm) + 2(8cm)
Simplify.
P = 20cm + 16cm
P= 36cm
Therefore, the perimeter of the rectangle is 36cm.
Example 2: Finding the Length when given Width and Perimeter of a Rectangle
Find the length of the rectangle below.
Solution for Example 2:
Start by writing down the given figures, the width (W = 5cm) and perimeter (P = 25cm).
Substitute 5cm for W and 25cm for P in the formula.
P = 2L + 2W
25cm = 2L + 2(5cm)
Simplify first by multiply 2 times the width (w = 5cm).
25cm = 2L +10cm
Continue by subtracting 10cm from both sides of the equation.
15cm = 2L
Divide both sides of the equation by 2 to find the length.
7.5cm = L
Therefore, the length of a rectangle with 25cm perimeter and 5cm width is 7.5cm.
TIP: Check the answer by plugging all figures into the formula.
Thank you for reading. We hope it’s effective! Always feel free to revisit this page if you ever have any questions about the perimeter of a rectangle.
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