Grade 5
  1. Number Sense and Place Value  1.1. Understanding Large Numbers  1.2. Place Value up to Millions  1.3. Comparing and Ordering Numbers  1.4. Rounding Whole Numbers  1.5. Expanded Form and Standard Form  1.6. Estimation in Calculations
  2. Operations with Whole Numbers  2.1. Addition of Large Numbers  2.2. Subtraction of Large Numbers  2.3. Multiplication Concepts and Strategies  2.4. Division Concepts and Strategies  2.5. Multi-Digit Multiplication  2.6. Long Division  2.7. Order of Operations
  3. Fractions  3.1. Introduction to Fractions  3.2. Equivalent Fractions  3.3. Simplifying Fractions  3.4. Comparing and Ordering Fractions  3.5. Addition and Subtraction of Fractions  3.6. Multiplication of Fractions  3.7. Division of Fractions  3.8. Mixed Numbers and Improper Fractions  3.9. Converting Between Improper Fractions and Mixed Numbers
  4. Decimals  4.1. Understanding Decimals  4.2. Place Value in Decimals  4.3. Comparing and Ordering Decimals  4.4. Rounding Decimals  4.5. Addition and Subtraction of Decimals  4.6. Multiplication of Decimals  4.7. Division of Decimals  4.8. Converting Decimals to Fractions and Vice Versa
  5. Measurement  5.1. Length Measurement (Metric and Customary Units)  5.2. Weight and Mass Measurement  5.3. Volume and Capacity Measurement  5.4. Area of Squares and Rectangles  5.5. Perimeter of Polygons  5.6. Time and Elapsed Time  5.7. Temperature  5.8. Understanding Metric Conversions
  6. Geometry  6.1. Types of Lines and Angles  6.2. Measuring Angles  6.3. Classifying Triangles  6.4. Properties of Quadrilaterals  6.5. Symmetry and Reflection  6.6. Transformations (Translation, Rotation, Reflection)  6.7. Coordinate Plane and Plotting Points  6.8. 3D Shapes and Their Properties  6.9. Nets of 3D Shapes  6.10. Understanding Congruence and Similarity
  7. Data and Probability  7.1. Introduction to Data Collection  7.2. Organizing Data (Tables and Tally Charts)  7.3. Graphs (Bar Graphs, Line Plots, Pictographs)  7.4. Mean, Median, and Mode  7.5. Range of Data  7.6. Introduction to Probability  7.7. Simple Events and Outcomes  7.8. Probability of Independent Events
  8. Ratios and Proportions  8.1. Understanding Ratios  8.2. Writing and Simplifying Ratios  8.3. Equivalent Ratios  8.4. Introduction to Proportions  8.5. Solving Proportion Problems
  9. Algebraic Thinking  9.1. Understanding Variables and Expressions  9.2. Writing Algebraic Expressions  9.3. Simplifying Expressions  9.4. Solving One-Step Equations  9.5. Understanding Patterns and Sequences  9.6. Using the Distributive Property
  10. Financial Literacy  10.1. Introduction to Money and Currency  10.2. Budgeting Basics  10.3. Saving and Spending  10.4. Understanding Interest  10.5. Basic Financial Planning  10.6. Simple vs. Compound Interest

Grade 5 → Measurement ↓


Perimeter of Polygons


Understanding the perimeter of polygons is an important part of learning geometry in class 5 maths. The perimeter is the total length around a polygon. To find it, you simply need to add the lengths of all the sides of the polygon. Let's understand this concept in more detail, explore different polygons and learn how their perimeter can be calculated.

What is the perimeter?

The word "perimeter" comes from the Greek words "peri," meaning "around," and "metron," meaning "to measure." So, perimeter means measuring around a shape. It's the distance around a two-dimensional shape. For polygons, which are flat, closed shapes with straight sides, the perimeter is the sum of the lengths of those sides.

Basic formula for perimeter

More generally, if a polygon has n sides, and the length of each side is denoted by a1, a2, ..., an, then the perimeter P is given by

P = a1 + a2 + ... + an

Visual examples of perimeter

Rectangle

A rectangle is a polygon with four sides where the opposite sides are equal. Therefore, if the length is l and the width is w, the perimeter P can be given as follows:

P = 2l + 2w
lAnd

For example, if the length of a rectangle is 8 cm and the width is 3 cm, then the perimeter can be calculated as follows:

P = 2(8) + 2(3) = 16 + 6 = 22 cm

Square

A square is a special type of rectangle where all sides are of equal length. If each side is s, then the perimeter P is simply:

P = 4s
S

Let each side of the square be 5 cm. We calculate the perimeter as follows:

P = 4(5) = 20 cm

Triangle

For a triangle that has three sides, the perimeter can be found by adding the lengths of the three sides. If the sides are a, b, and c, then the perimeter P is:

P = a + b + c
CAB

For example, the perimeter of a triangle with sides 6 cm, 8 cm and 10 cm will be:

P = 6 + 8 + 10 = 24 cm

Pentagon

A pentagon is a five-sided polygon. If all sides are of equal length, it is called a regular pentagon. If the length s of one side is known, the perimeter of a regular pentagon can be easily calculated:

P = 5s

If each side of the pentagon is 4 cm, then:

P = 5(4) = 20 cm

More examples and exercises

Let's work through some more examples of perimeter calculations for different types of polygons.

Example 1: Irregular quadrilateral

Consider an irregular quadrilateral whose sides have lengths 5 cm, 7 cm, 4 cm, and 6 cm. The perimeter will be calculated as follows:

P = 5 + 7 + 4 + 6 = 22 cm

Example 2: Hexagon

For a regular hexagon (a six-sided polygon with each side of equal length), if each side is 3 cm, the perimeter is:

P = 6(3) = 18 cm

Example 3: Octagon

Consider a regular octagon with each side measuring 2 cm. The perimeter can be calculated as:

P = 8(2) = 16 cm

Why is it important to learn about perimeter?

Learning how to calculate perimeter has practical applications in real life. For example, if you need to build a fence around the garden or put a new frame around a picture, knowing how to calculate perimeter will help you determine how much material you need.

Understanding perimeter also enhances problem-solving and critical thinking skills. Students get practice adding numbers, understanding the properties of different shapes, and applying these skills to everyday scenarios.

Conclusion

Calculating the perimeter of polygons is a foundational concept in mathematics. By understanding and applying it, students can better understand the world around them, preparing them for more complex mathematical concepts in the future.

Revisit these examples and try more practice problems to get comfortable with finding the perimeter of different polygons. Always remember to add up all side lengths correctly, and with practice, it will become second nature!


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Perimeter of Polygons

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