Triangle Perimeter Practice Problems & Solutions

Master triangle perimeter calculations with step-by-step practice problems. Learn formulas for equilateral, isosceles, and scalene triangles with interactive exercises.

📚Practice Calculating Triangle Perimeters
  • Calculate perimeter by adding all three sides of any triangle
  • Apply perimeter formulas for equilateral triangles using one side length
  • Solve isosceles triangle perimeter problems with base and equal sides
  • Work with different units of measurement (mm, cm, meters)
  • Find missing side lengths when perimeter is given
  • Apply triangle perimeter concepts to real-world measurement problems

Understanding Perimeter

Complete explanation with examples

What is the perimeter?

The perimeter indicates the distance we will walk if we start from a certain point, complete a full lap, and return exactly to the starting point.
For example, if we are asked what the perimeter of the waist is, we will take a tape measure and measure the perimeter from a certain point until completing a full lap and returning to the same point from which we started the measurement.
It works exactly the same way in mathematics. The perimeter of any shape is the distance from a specific point back to it after having completely surrounded it.
If this is our figure:

What is the perimeter

Its perimeter will be the distance we cover if we travel along its line from a certain point, and return to it after making a full lap. Imagine that you are surrounding the figure:

Detailed explanation

Practice Perimeter

Test your knowledge with 80 quizzes

AB = 5

CD = 7

AC = 4

BD = 4

Calculate the perimeter of the rectangle.

555444777444AAABBBDDDCCC

Examples with solutions for Perimeter

Step-by-step solutions included
Exercise #1

Look at the rectangle below.

Side AB is 2 cm long and side BC has a length of 7 cm.

What is the perimeter of the rectangle?
222777AAABBBCCCDDD

Step-by-Step Solution

Given that in a rectangle every pair of opposite sides are equal to each other, we can state that:

AB=CD=2 AB=CD=2

AD=BC=7 AD=BC=7

Now we can add all the sides together and find the perimeter:

2+7+2+7=4+14=18 2+7+2+7=4+14=18

Answer:

18 cm

Video Solution
Exercise #2

Look at the rectangle below.

Side AB is 4.8 cm long and side AD has a length of 12 cm.

What is the perimeter of the rectangle?
4.84.84.8121212AAABBBCCCDDD

Step-by-Step Solution

In the drawing, we have a rectangle, although it is not placed in its standard form and is slightly rotated,
but this does not affect that it is a rectangle, and it still has all the properties of a rectangle.
 
The perimeter of a rectangle is the sum of all its sides, that is, to find the perimeter of the rectangle we will have to add the lengths of all the sides.
We also know that in a rectangle the opposite sides are equal.
Therefore, we can use the existing sides to complete the missing lengths.
 
4.8+4.8+12+12 =
33.6 cm

Answer:

33.6 cm

Video Solution
Exercise #3

Look at the rectangle below.

Side DC has a length of 1.5 cm and side AD has a length of 9.5 cm.

What is the perimeter of the rectangle?

1.51.51.5AAABBBCCCDDD9.5

Step-by-Step Solution

Since in a rectangle every pair of opposite sides are equal to each other, we can state that:

AD=BC=9.5 AD=BC=9.5

AB=CD=1.5 AB=CD=1.5

Now we can add all the sides together and find the perimeter:

1.5+9.5+1.5+9.5=19+3=22 1.5+9.5+1.5+9.5=19+3=22

Answer:

22 cm

Video Solution
Exercise #4

Look at the triangle below:

666888101010

What is the perimeter of the triangle?

Step-by-Step Solution

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

6+8+10=14+10=24 6+8+10=14+10=24

Answer:

24

Video Solution
Exercise #5

Given the triangle:

777111111131313

What is its perimeter?

Step-by-Step Solution

The perimeter of a triangle is equal to the sum of all its sides together:

11+7+13=11+20=31 11+7+13=11+20=31

Answer:

31

Video Solution

Frequently Asked Questions

Everything you need to know about Perimeter

What is the formula for finding the perimeter of a triangle?

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The perimeter of a triangle is found by adding all three sides together: P = a + b + c, where a, b, and c are the lengths of the three sides. This formula works for all types of triangles including scalene, isosceles, and equilateral triangles.

How do you find the perimeter of an equilateral triangle?

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For an equilateral triangle, all three sides are equal in length. The formula is P = 3a, where 'a' is the length of one side. Simply multiply the side length by 3 to get the perimeter.

What information do I need to find an isosceles triangle's perimeter?

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For an isosceles triangle, you need the length of the base and the length of one of the two equal sides. The formula is P = base + 2(equal side), since two sides have the same measurement.

Can triangle perimeter be measured in different units?

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Yes, triangle perimeter can be measured in various units including: • Millimeters (mm) • Centimeters (cm) • Meters (m) • Inches or feet Remember to convert units when necessary: 1 cm = 10 mm, 1 meter = 100 cm.

How do I solve triangle perimeter word problems?

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Follow these steps: 1) Identify what type of triangle you have, 2) Write down the known side lengths, 3) Apply the appropriate perimeter formula, 4) Add the measurements carefully, 5) Include the correct units in your final answer.

What's the difference between perimeter and area of a triangle?

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Perimeter measures the distance around the outside of a triangle by adding all three sides together. Area measures the space inside the triangle using the formula A = ½ × base × height. Perimeter is measured in linear units (cm, m) while area uses square units (cm², m²).

Can I find a missing side if I know the triangle's perimeter?

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Yes, if you know the perimeter and two side lengths, you can find the third side using: missing side = perimeter - (side 1 + side 2). This works because the perimeter equals the sum of all three sides.

What are common mistakes when calculating triangle perimeter?

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Common errors include: forgetting to add all three sides, mixing up different units of measurement, confusing perimeter with area formulas, and making arithmetic mistakes when adding the side lengths. Always double-check your addition and units.

More Perimeter Questions

Click on any question to see the complete solution with step-by-step explanations

Perimeter of a Rectangle

Calculate the Perimeter: Finding Border Length in a 2×4×5 Rectangular Diagram Calculate Parallelogram Area: Rectangle with Perimeter 24 Inside Calculate the Perimeter: Rectangle Composed of Two Equal Squares Calculate Rectangle Area: Given Perimeter 30cm and Height 5cm Find the Rectangle Perimeter: When 4cm Square Equals 1cm-Sided Rectangle Area

Perimeter of a Parallelogram

Calculate Parallelogram Area: 38cm Perimeter with Proportional Sides Calculate Parallelogram Height: Area 24 cm², Perimeter 24 cm with Double-Length Side Calculate Parallelogram Perimeter: Given Area 39 cm² and Height 3 cm Calculate Parallelogram Perimeter: Using Side Lengths 4 and 6 Calculate Parallelogram Perimeter: Using Side Lengths 7 and 10

Perimeter of a Trapezoid

Calculate Trapezoid Perimeter: Inside an Isosceles Triangle with Height 8 Compare Two Trapezoids: Analyzing Measurements x+5, 17, and Variable y Compare Trapezoids: Are Two Trapezoids with Sides x and x+16 Congruent? Trapezoid Perimeter: Finding the Total Length with a 1.5 Base Ratio Calculate the Missing Side in a Trapezoid with 25cm Perimeter

Circumference

Calculate Parallelogram Area: Circle with Circumference 25.13 and Tangent Points Circle-Parallelogram Tangency Problem: Finding Area of Blue Regions with 25.13 Circumference Calculate Circle Area When Rectangle Area = 28X: Geometric Relationship Problem Calculate Average Speed: 5 Laps on a 300-Meter Radius Circular Track Calculate Circle Radius from Circumference 31.41: Using C = 2πr

Perimeter of a Triangle

Calculate the Perimeter of an Equilateral Triangle with 5-Unit Sides Find X in an Equilateral Triangle with 33cm Perimeter Calculate the Perimeter: Isosceles Triangle with Sides 6 and Base 4 Solve for X: Finding the Side Length in an Isosceles Triangle with Perimeter 50 Triangle Side Lengths: Solve for X When 2X + 3X + 3.5X = 17

Continue Your Math Journey

Master Perimeter first, then advance to these related topics that build on your fraction skills

Suggested Topics to Practice in Advance

AreaThe sides or edges of a triangleTriangle HeightThe Sum of the Interior Angles of a TriangleExterior angles of a triangleTypes of TrianglesObtuse TriangleEquilateral triangleIdentification of an Isosceles TriangleScalene triangleAcute triangleIsosceles triangleThe Area of a TriangleArea of a right triangleArea of Isosceles TrianglesArea of a Scalene TriangleArea of Equilateral TrianglesAreas of Polygons for 7th GradeRight TriangleMedian in a triangleCenter of a Triangle - The Centroid - The Intersection Point of MediansHow do we calculate the area of complex shapes?How to calculate the area of a triangle using trigonometry?All terms in triangle calculation

Topics Learned in Later Sections

TrianglePerimeter of a triangleHow do we calculate the perimeter of polygons?

Practice by Question Type

Choose your preferred learning style and practice format for fraction problems
Applying the formula A shape consisting of several shapes (requiring the same formula) Calculate The Missing Side based on the formula Calculating parts of the circle Finding Area based off Perimeter and Vice Versa Identifying and defining elements Identify the greater value Increasing a specific element by addition of.....or multiplication by....... Subtraction or addition to a larger shape Using additional geometric shapes Using Pythagoras' theorem Using variables Verifying whether or not the formula is applicable Worded problems Applying the formula Calculate The Missing Side based on the formula Finding Area based off Perimeter and Vice Versa Using additional geometric shapes Using the properties of the perimeter of the parallelogram Using variables Applying the formula Comprehension exercises Finding Area based off Perimeter and Vice Versa Using congruence and similarity Using Pythagoras' theorem Using variables Applying the formula Calculate The Missing Side based on the formula Comparison between 2 of the same shape with an identical perimeter Finding Area based off Perimeter and Vice Versa Using variables Applying the formula Finding Area based off Perimeter and Vice Versa The Perimeter of a Triangle