Perimeter of an Equilateral Triangle – Formulas and Examples

The perimeter of an equilateral triangle is the total length covered by the outline of the figure. We can find the perimeter by adding all the lengths of the sides of the triangle. Since the lengths of the sides of an equilateral triangle are equal, we simply need to know the length of one side to find the perimeter.

Here, we will learn about the formula that we can use to calculate the perimeter of equilateral triangles. In addition, we will apply this formula to solve some problems.

GEOMETRY
formula for the perimeter of an equilateral triangle

Relevant for

Learning about the perimeter of an equilateral triangle with examples.

See examples

GEOMETRY
formula for the perimeter of an equilateral triangle

Relevant for

Learning about the perimeter of an equilateral triangle with examples.

See examples

Formula for the perimeter of an equilateral triangle

The perimeter of an equilateral triangle is the measure of the total length of its limits. To find the perimeter, we have to add the lengths of all the sides. Since an equilateral triangle has all the sides of the same length, we only need the length of one side. We can use the following formula:

p=3a

where a is the length of one side of the triangle.

diagram of an equilateral triangle

Perimeter of an equilateral triangle – Examples with answers

In the following examples, we use the formula for the perimeter of equilateral triangles to get the answer. Try to solve the exercises yourself and look at the solution to check your answer.

EXAMPLE 1

An equilateral triangle has sides of length 5 m. What is the perimeter?

We can use the perimeter formula with the value a=5. Therefore, we have:

p=3a

p=3(5)

p=15

The perimeter of the triangle is 15 m.

EXAMPLE 2

What is the perimeter of an equilateral triangle that has sides of length 8 m?

We plug a=8 into the perimeter formula:

p=3a

p=3(8)

p=24

The perimeter of the triangle is 24 m.

EXAMPLE 3

If an equilateral triangle has sides of length 15 cm, what is its perimeter?

We use the value a=15 in the formula:

p=3a

p=3(15)

p=45

The perimeter of the triangle is 45 cm.

EXAMPLE 4

An equilateral triangle has a perimeter of 39 m. What is the length of its sides?

In this case, we start with the perimeter and we want to find the length of one of the sides of the triangle. Therefore, we use the perimeter formula and solve for a:

p=3a

39=3a

a=13

The length of the sides of the triangle is 3 m.

EXAMPLE 5

What is the length of the sides of an equilateral triangle that has a perimeter of 102 m?

We use the perimeter formula with p=102 and solve for a:

p=3a

102=3a

a=34

The length of one side of the triangle is 34 m.


Perimeter of an equilateral triangle – Practice problems

Practice using the formula for the perimeter of equilateral triangles to solve the following problems. Check out the solved exercises above in case you need help.

What is the perimeter of an equilateral triangle that has sides of length 11m?

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What is the perimeter of an equilateral triangle that has sides of length 23m?

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What is the length of the sides of an equilateral triangle with perimeter 75 m?

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An equilateral triangle has a perimeter of 93m. What is the length of its sides?

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See also

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