Understanding perimeter involves knowing how to measure the distance around different shapes. Each shape has its unique formula to find the perimeter. Let’s look at a few of the common shapes and their formulas:

• Square or rectangle: To calculate the perimeter of a square or rectangle, add up all its sides. For a square, where all sides are equal, you simply multiply one side by 4 (P = 4s). In a rectangle, you’ll add up the two longer sides and the two shorter sides, or double the length and add it to double the width (P = 2l + 2w).
  
  
• Circle: To measure the distance around a circle, or its perimeter, you use the perimeter formula two times pi times the radius (P = 2πr). Remember, the radius is the straight line from the circle’s centre to its edge.
  
  
• Triangle: The perimeter of a triangle is the total of all its three sides. Just add side ‘a’ to side ‘b’ to side ‘c’, and there you have it (P = a + b +c)!
  
  
• Parallelogram: The perimeter of a parallelogram is found by adding up the lengths of all its sides. If the opposite sides are equal, then you can double one side and add it to double the other side (P = 2(a + b)).
  
  
• Trapezium: For a trapezium, you simply add all its four sides together to get its perimeter (P = a + b + c + d).