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Perimeter of a Triangle
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The perimeter of a triangle is found the same way as the perimeter of a rectangle. It is the measure of the outside edges. In this course, we will give you the lengths of the sides of a triangle in order to find the perimeter. Finding the lengths of the sides is outside the scope of this course.

Here are some vocabulary to review for this lesson.

• Triangle = a 3 sided shape
• Equilateral Triangle = a triangle whose sides are all the same length
• Perimeter of a triangle = add all the lengths of the sides together.
Perimeter of a Triangle

### Practice Problems

1. Find the perimeter of a triangle with sides a, b, and c, where a = 14, b = 20, and c = 8. (
Solution
Solution:
42
)
2. Find the perimeter of a triangle with sides a, b, and c, where a=12.5, b=13.8, and c=16.3. Round your answer to the nearest tenth. (
Solution
Solution:
42.6
)
3. Oliver is building a garden that is in the shape of a triangle with sides of length 9 m, 12 m, and 5 m. If Oliver wants to build a fence around the perimeter of his garden, how many meters of fencing does he need to buy? (
Solution
Solution: 26m
Details:
Oliver wants to put up a fence around his garden so he needs to find out how many meters of fencing he needs to go around the entire garden. To find out how much fencing he needs, he will have to find the perimeter of his garden. Since the garden is shaped like a triangle, the perimeter is the sum of the lengths of all three sides.

$$12 + 5 + 9 = 26$$

So Oliver will need to purchase 26 meters of fencing.
)
4. Gabriel rides his bike every morning and follows a path that forms a triangle with distances of 8.4km, 12.5km, and 9.2km. When Gabriel finishes his bike ride, how far has he ridden? Round to the nearest tenth. (
Solution
Solution:
30.1km
)
5. An equilateral triangle has sides of length 6 m. Find the perimeter of this equilateral triangle. (
Solution
Solution: 18m
Details:
The triangle is an equilateral triangle. That means that all three sides have the same length. In this case, all three sides are 6 m long. To find the perimeter of an equilateral triangle, we need to add all three side lengths together.

$$6 + 6 + 6 = 18$$

So the perimeter of the triangle is 18 meters long.
)
6. A triangle has sides with lengths a, b, and c. The length of side a is 15 inches, and side b is two more inches than side a. If the perimeter of the triangle is equal to 40 inches, what is the length of side c? (
Video Solution
Solution: 8in
Details:

(Video Source | Transcipt)
)
7. A triangular slice of pizza has a perimeter of 45 centimeters (cm). One side of the pizza slice is 18 cm with an adjacent side that is half the length of the first side. What is the length of the third side? (
Video Solution
Solution: 18cm
Details:

(Video Source | Transcript)
)

### Need More Help?

1. Study other Math Lessons in the Resource Center.
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