VidaaraPlay
Door 13 · Grade 3

📏 Perimeter

Perimeter = total distance around the shape

▶ Play Door 13

Find Perimeter by Adding Sides

Perimeter is the total distance around the outside of a shape.
Perimeter = sum of all side lengths
• Rectangle: P = 2 x (length + width)
• Square: P = 4 x side
• Any shape: add up all sides

Worked example

Problem: Rectangle: length 7 m, width 4 m. Find the perimeter.

  1. P = 7+4+7+4 = 22 m.
  2. Or use formula: P = 2 x (7+4) = 2 x 11 = 22 m.

Answer: Or use formula: P = 2 x (7+4) = 2 x 11 = 22 m.

Find the Missing Side Given Perimeter

If you know the perimeter and some side lengths, subtract to find the missing side.
Missing side = Perimeter - sum of known sides
For rectangles: Perimeter = 2 x (Length + Width), so Length + Width = Perimeter / 2.

Worked example

Problem: Square perimeter is 36 cm. What is each side?

  1. Square side = Perimeter / 4 = 36 / 4 = 9 cm.

Answer: Square side = Perimeter / 4 = 36 / 4 = 9 cm.