Perimeter

Perimeter

Perimeter is simply the length around a two dimensional figure. To find the perimeter we simply add the length of all sides. For the following figures, you can use the formulas below.

Square: P = 4s

Rectangle: P = 2L + 2W

Triangle: P = a + b + c

Example 1:

Find the perimeter of a square if each side has a length of 5in.

Solution: s = 5in. Therefore the perimeter is P =4s = 4 x 5in = 20in.

Example 2:

Find the perimeter of a rectangle if the length is 6in. and the width is 5in.

Solution: L = 6in and W = 5in. Therefore, the perimeter is P = 2L + 2W = 2x6in + 2x5in = 12in + 10in = 22in.

Example 3:

Find the perimeter of a triangle with the following dimensions:

Side 1 = 3in

Side 2 = 4in

Side 3 = 5in

Solution: a = 3in, b = 4in, and c = 5in. Therefore, the perimeter is

P = a + b +c = 3in + 4in + 5in = 12in.

Example 4:

Find the perimeter of the figure below:

7 in

10 in 12 in

18 in

Solution: P = 7in + 12in + 18in + 10in = 47in

Guided Solution 1:

Find the perimeter of a square if each side has a length of 8in.

  1. What is the formula to find the perimeter of a square?
  2. s = _____
  3. What is the perimeter of the square?

Guided Solution 2:

Find the perimeter of a rectangle if the length is 8in and the width is 7in.

  1. What is the formula to find the perimeter of a rectangle?
  2. L = _____
  3. W = _____
  4. What is the perimeter of the rectangle?

Guided Solution 3:

Find the perimeter of a triangle with the following dimensions:

Side 1 = 6in

Side 2 = 8in

Side 3 = 10in

  1. What is the formula to find the perimeter of a triangle?
  2. a = _____
  3. b = _____
  4. c = _____
  5. What is the perimeter of the triangle?