115 LearnersLast updated on August 5th, 2025
Math Formula for Perimeter of Triangle Formulas
In geometry, the perimeter of a triangle is the total length around the triangle. It is calculated by adding the lengths of all three sides. In this topic, we will learn the formulas for finding the perimeter of different types of triangles, suitable for students.
List of Math Formulas for Perimeter of Triangle
The perimeter of a triangle is calculated by summing the lengths of its sides. Let's learn the formulas to calculate the perimeter of different types of triangles.
Math Formula for Perimeter of a General Triangle
The perimeter of a general triangle is the sum of the lengths of its three sides.
Perimeter formula:
P = a + b + c, where a, b, and c are the lengths of the sides of the triangle.
Math Formula for Perimeter of an Equilateral Triangle
An equilateral triangle has all three sides of equal length. The formula for the perimeter of an equilateral triangle is:
Perimeter formula:
P = 3a, where a is the length of a side of the triangle.
Math Formula for Perimeter of an Isosceles Triangle
An isosceles triangle has two sides of equal length. The formula for the perimeter of an isosceles triangle is:
Perimeter formula:
P = 2a + b, where a is the length of the equal sides, and b is the base of the triangle.
Importance of Perimeter of Triangle Formulas
In math and real life, knowing how to calculate the perimeter of a triangle is important for various applications. Here are some reasons why the perimeter formulas are important:
Understanding perimeter helps in solving real-world problems involving construction, fencing, and design.
Learning these formulas helps students strengthen their geometry skills, which are applicable in higher-level math and practical situations.
Tips and Tricks to Memorize Perimeter of Triangle Formulas
Students often find geometry formulas challenging. Here are some tips and tricks to master the perimeter formulas:
Remember that the perimeter is simply the total length around the triangle, so you need to add all sides.
For equilateral triangles, think "3 sides the same," hence "3 times the side."
Use flashcards to memorize the formulas and rewrite them for quick recall.
Common Mistakes and How to Avoid Them While Using Perimeter of Triangle Formulas
Students make errors when calculating the perimeter of triangles. Here are some mistakes and ways to avoid them:
Mistake 1
Confusing Perimeter with Area
Students sometimes confuse the perimeter with the area, which leads to incorrect calculations. To avoid this error, remember that the perimeter is the sum of all sides, while the area is the space within.
Mistake 2
Incorrectly Adding Side Lengths
When adding side lengths, calculation errors often occur. To avoid these errors, double-check each side length before performing the addition.
Mistake 3
Using Wrong Formula for Triangle Type
Students sometimes use the wrong formula for a given triangle type. Ensure that the formula matches the specific triangle, whether it is equilateral, isosceles, or scalene.
Mistake 4
Forgetting to Use Units
Students often forget to include units in their final answer, which can lead to confusion. Always express the perimeter with the correct unit of measurement.
Mistake 5
Misidentifying Triangle Sides
When identifying the sides of a triangle, students sometimes make errors. To avoid this, carefully label each side and ensure the correct use of the formula.
Examples of Problems Using Perimeter of Triangle Formulas
Problem 1
Find the perimeter of a triangle with sides 5 cm, 7 cm, and 9 cm.
The perimeter of the triangle is 21 cm.
Explanation
To find the perimeter, add all the side lengths: 5 + 7 + 9 = 21 cm.
Problem 2
Calculate the perimeter of an equilateral triangle with a side length of 4 cm.
The perimeter of the equilateral triangle is 12 cm.
Explanation
Since all sides are equal, the perimeter is 3 times the side length: 3 × 4 = 12 cm.
Problem 3
Find the perimeter of an isosceles triangle with equal sides of 6 cm and a base of 8 cm.
The perimeter of the isosceles triangle is 20 cm.
Explanation
Perimeter = 2 × 6 + 8 = 12 + 8 = 20 cm.
Problem 4
A triangular garden has sides measuring 15 m, 20 m, and 25 m. What is the perimeter?
The perimeter of the garden is 60 m.
Explanation
To find the perimeter, add all the side lengths: 15 + 20 + 25 = 60 m.
Problem 5
Determine the perimeter of an equilateral triangle with each side measuring 10 m.
The perimeter of the equilateral triangle is 30 m.
Explanation
Since all sides are equal, the perimeter is 3 times the side length: 3 × 10 = 30 m.
FAQs on Perimeter of Triangle Formulas
1.What is the perimeter formula for a general triangle?
2.What is the formula for the perimeter of an equilateral triangle?
3.How to find the perimeter of an isosceles triangle?
4.What is the perimeter of a triangle with sides 8 cm, 12 cm, and 15 cm?
5.What is the perimeter of an equilateral triangle with side 7 m?
Glossary for Perimeter of Triangle Formulas
- Perimeter: The total length around a figure or shape, specifically the sum of the lengths of its sides.
- Equilateral Triangle: A triangle with all three sides of equal length.
- Isosceles Triangle: A triangle with two sides of equal length.
- Scalene Triangle: A triangle with all sides of different lengths.
- Units: The standard measures used to express the length of the sides, such as centimeters or meters.
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Jaskaran Singh Saluja
About the Author
Jaskaran Singh Saluja is a math wizard with nearly three years of experience as a math teacher. His expertise is in algebra, so he can make algebra classes interesting by turning tricky equations into simple puzzles.
Fun Fact
: He loves to play the quiz with kids through algebra to make kids love it.
