Where l = length of the given rectangle, b = breadth of the given rectangle.įor the given rectangle, l = 12 cm, b = 5 cm. We know that the perimeter of a rectangle is given by Perimeter = 2 cm + 3 cm + 3 cm + 4 cm + 5 cm = 18 cmĮxample 3: What will be the perimeter of a rectangle with length 12 cm and breadth 5 cm? The perimeter of this pentagon will be given by the sum of all its sides. The given shape is an irregular pentagon. We know that the perimeter of a triangle is given byĮxample 2: Calculate the perimeter of the following figure. Perimeter of irregular polygon = sum of all sides.Įxample 1: What is the perimeter of the given figure? Since the sides of an irregular polygon may not all be the same in length, we use the general formula to find the perimeter of an irregular shape. The given table summarizes the formulas to find the perimeter of some regular polygons: Perimeter of An Irregular Shape Therefore, Perimeter = number of sides ✕ length of one side The perimeter of the given regular pentagon can be calculated as follows: Perimeter of regular polygon = sum of all its sides = number of sides ✕ length of one side.įor example, look at the given regular pentagon. We know that the length of each side of a regular polygon is the same. How to Find Perimeter Perimeter of a Regular Shape For example, when putting up Christmas lights around the house or when we want to put a fence around the backyard, we find its perimeter to know the length of wire we will need. Designed for a third grade math curriculum, this colorful worksheet helps bring to life a fundamental geometry concept. They then calculate the perimeter of regular and irregular shapes and solve two word problems. Students learn that the perimeter of a polygon can be found by adding the lengths of its sides together. We often use the concept of perimeter in real life. Children practice calculating the perimeter of a variety of polygons in this geometry basics worksheet. Perimeter of the given shape = 6 cm + 5 cm + 5 cm + 4 cm + 3 cm = 23 cm. Perimeter of a shape = Sum of all its sides, Let’s try to calculate the perimeter of the following shape: It is measured in linear units of measurement like centimeters, meters, inches, or feet. The perimeter of a shape is determined by adding the length of all the sides and edges enclosing the shape. įor more teaching and learning support on Geometry our GCSE maths lessons provide step by step support for all GCSE maths concepts.In geometry, the perimeter of a shape is defined as the total length of its boundary. Looking forward, students can then progress to additional geometry worksheets, for example an area of a rectangle worksheet or angles in polygons worksheet. Perimeter word problems could require students to calculate the length of a fence or boundary. More complex problems could include using subtraction to find a missing side length, or to use 2D shape properties to work out the side lengths and then find area. For example, if finding the perimeter of rectilinear shapes, it is important that students carefully identify the outside edges of the shape and don’t just add up all the side lengths they can see. It is therefore important that students can work confidently with metric units and decimals.Ĭompound shapes (shapes made from two or more simple shapes) can be more tricky. Sometimes, students are required to measure the length of the sides from an accurately drawn diagram and then calculate the perimeter as above. The process is the same for irregular shapes and for the perimeter of polygons such as pentagons or hexagons. For the perimeter of a rectangle or other quadrilaterals such as a rhombus or a parallelogram we need to add up all of the side lengths to find the total. The perimeter of a 2D shape is the distance all the way around the outside of it.
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