Calculate the Perimeter of an Equilateral Triangle with 5-Unit Sides

Perimeter Calculation with Equal Side Lengths

Given an equilateral triangle:

555

What is its perimeter?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Calculate the perimeter of the triangle
00:02 The perimeter equals the sum of the triangle's sides
00:07 The triangle is equilateral hence all sides equal 5
00:11 Substitute in the relevant values and proceed to solve
00:15 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given an equilateral triangle:

555

What is its perimeter?

2

Step-by-step solution

Since the triangle is equilateral, that is, all sides are equal to each other.

The perimeter of the triangle is equal to the sum of all sides together, the perimeter of the triangle in the drawing is equal to:

5+5+5=15 5+5+5=15

3

Final Answer

15

Key Points to Remember

Essential concepts to master this topic
  • Definition: Perimeter equals sum of all side lengths
  • Technique: Multiply side length by number of sides: 5×3=15 5 \times 3 = 15
  • Check: Add each side individually to verify: 5+5+5=15 5 + 5 + 5 = 15

Common Mistakes

Avoid these frequent errors
  • Confusing perimeter with area calculation
    Don't use formulas for area when finding perimeter = wrong answer entirely! Area measures space inside the shape, while perimeter measures distance around the edges. Always add up all side lengths for perimeter.

Practice Quiz

Test your knowledge with interactive questions

Is the triangle in the drawing a right triangle?

FAQ

Everything you need to know about this question

What does 'equilateral' actually mean?

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Equilateral means all sides have the same length. So if one side is 5 units, then all three sides are 5 units each.

Is there a shortcut for finding perimeter of equilateral triangles?

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Yes! Since all sides are equal, you can multiply the side length by 3. For this triangle: 5×3=15 5 \times 3 = 15 units.

Why can't the answer be 5 or 10?

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The answer 5 is just one side, not the whole perimeter. The answer 10 would only be two sides. You need all three sides for the complete perimeter.

What if the triangle wasn't equilateral?

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For any triangle, you still add all three side lengths. The difference is that non-equilateral triangles have different side lengths, so you can't use the multiplication shortcut.

How do I remember what perimeter means?

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Think of walking around the shape! Perimeter is the total distance you'd walk if you traced around the outside edges of the triangle.

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