1. Perimeter
of Triangles

2. This powerpoint presentation will teach you about perimeter of triangles.

3. When you see this symbol at the top of the screen, the answer is given – but you still must write it on your paper if the problem number is on your worksheet.
Be careful though, not every problem number is on your worksheet!

4. When you see this symbol at the top of the screen, it’s your turn to try a problem. You’ll be turning your paper in, so work carefully. If you have any questions, make sure you ask them!

5. 1. What is perimeter?
The perimeter of any figure is the sum of the lengths of the sides.

6. 2. What is the perimeter of the triangle below? (each
measurement is in inches) 8 5 11 =
24 inches

7. 3. What is the perimeter of the triangle below? (each
measurement is in feet) 12 9 15

8. 4. What is the perimeter of the triangle below? (each
measurement is in centimeters) 19 12 13

9. 5. What is the perimeter of the triangle below? (each
measurement is in inches) 14 19

10. 6. The perimeter of the triangle below is 30 centimeters
6. The perimeter of the triangle below is 30 centimeters. What is the length of the missing side? 9 10 =
11 centimeters

11. 7. The perimeter of the triangle below is 68 feet
7. The perimeter of the triangle below is 68 feet. What is the length of the missing side? 24

12. An isosceles triangle has a
perimeter of 25 inches and the base is 9 inches. What is the length of each leg?
Sketch an isosceles triangle 9

13. x 9 Label the legs with x Since the perimeter is 25 inches,
8. (continued)
Label the legs with x 9 x
Since the perimeter is 25 inches,
x + x + 9 = 25
x = 8 inches
2x + 9 = 25
2x = 16

14. 9. An isosceles triangle has a perimeter of 50 feet and the base is 16 feet. What is the length of each leg?

15. 10. An isosceles triangle has a perimeter of 67 cm
10. An isosceles triangle has a perimeter of 67 cm. The length of each leg is 19 cm. What is the length of the base?

16. 11. An isosceles triangle has a
perimeter of 30 inches. The
length of one leg is 9 inches.
What is the length of the base?

17. 12. An equilateral triangle has
a perimeter of 42 cm. What is
the length of each side?

18. 13. An equilateral triangle has
a perimeter of 51 feet. What is
the length of each side?

19. 14. The two equilateral triangles below
each have a perimeter of 72 inches.
They are pushed together to form a
4-sided figure (side BC of ∆ABC lined
up with side BC of ∆BCD). What is the
perimeter of the 4 sided figure? B B A D C C

20. 15. An octagon is made up of 8
isosceles triangles each with a
perimeter of 26 cm. The legs of each
isosceles triangle measure 8 cm. What
is the perimeter of the octagon?

21. 16. The perimeter of the triangle below is 21 inches. Find x and the
length of each side.
2x+4
5x-5
3x+1

22. 17. The perimeter of the triangle is 38 cm. find x and the length of
each side.
3x – 1
4x + 3
7x – 6
18. What kind of triangle is it?

23. 19. The perimeter of the triangle is 21 feet. Find x and the length of
each side.
2x – 3
x + 2
3x – 8
20. What kind of triangle is it?