The perimeter of the rectangle shown is AB + BC + CD + DA = 8 + 5 + 8 + 5 = 26 units
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Perimeter of a rectangle can also be found using the formula 2(l + w), where l is the length and w is the width.

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Solved Example on Perimeter

Ques: ABC is an equilateral triangle and the perimeter of triangle ABC is 12 in. Find the measure of each side.

Choices:

A. 36 in.
B. 4 in.
C. 12 in.
D. 6 in.
Correct Answer: B

Solution:

Step 1: In triangle ABC, AB = BC = CA
Step 2: Let AB = BC = CA = x in.
Step 3: Perimeter of â–³ABC = AB + BC + CA
Step 4: AB + BC + CA = 12
Step 5: x + x + x = 12 [Substitute AB = BC = CA = x.]
Step 6: 3x = 12 [Combine like terms.]
Step 7: [Divide each side by 3.]
Step 8: x = 4 [Simplify.]
Step 9: AB = BC = CA = 4 in.
Step 10: So, the measure of each side is 4 in.