Grade 7
  1. Number System  1.1. Integers  1.1.1. Properties of Integers  1.1.2. Operations on Integers  1.1.3. Additive and Multiplicative Inverses  1.1.4. Applications of Integers  1.2. Rational Numbers  1.2.1. Definition of Rational Numbers  1.2.2. Properties of Rational Numbers  1.2.3. Operations on Rational Numbers  1.2.4. Standard Form of Rational Numbers  1.3. Decimals  1.3.1. Operations on Decimals  1.3.2. Converting Between Fractions and Decimals  1.4. Powers and Exponents  1.4.1. Laws of Exponents  1.4.2. Simplifying Expressions with Exponents  1.4.3. Scientific Notation  1.5. Roots  1.5.1. Square Roots  1.5.2. Cube Roots
  2. Algebra  2.1. Expressions  2.1.1. Algebraic Expressions  2.1.2. Simplifying Expressions  2.1.3. Evaluating Expressions  2.2. Linear Equations  2.2.1. Solving Simple Equations  2.2.2. Applications of Linear Equations  2.3. Algebraic Identities  2.3.1. Expanding Using Identities  2.3.2. Simplifying Using Identities
  3. Ratio and Proportion  3.1. Ratios  3.1.1. Understanding Ratios  3.1.2. Simplifying Ratios  3.1.3. Equivalent Ratios  3.2. Proportion  3.2.1. Concept of Proportion  3.2.2. Direct Proportion  3.2.3. Inverse Proportion  3.3. Unitary Method  3.3.1. Solving Problems Using the Unitary Method
  4. Geometry  4.1. Lines and Angles  4.1.1. Types of Angles  4.1.2. Pairs of Angles  4.1.3. Properties of Parallel Lines and a Transversal  4.1.4. Angle Bisectors  4.2. Triangles  4.2.1. Types of Triangles  4.2.2. Angle Sum Property  4.2.3. Exterior Angle Property  4.2.4. Pythagoras Theorem  4.3. Congruence of Triangles  4.3.1. Criteria for Congruence  4.3.2. Applications of Congruence  4.4. Quadrilaterals  4.4.1. Types of Quadrilaterals  4.4.2. Properties of Parallelograms  4.4.3. Special Quadrilaterals  4.4.4. Properties of Rectangles and Rhombuses
  5. Mensuration  5.1. Perimeter and Area  5.1.1. Perimeter of Plane Figures  5.1.2. Area of Plane Figures  5.1.3. Area of a Trapezium  5.1.4. Area of a Parallelogram  5.1.5. Area of a Circle  5.1.6. Area of Composite Figures  5.2. Surface Area and Volume  5.2.1. Cubes and Cuboids  5.2.2. Surface Area of Cylinders  5.2.3. Volume of Prisms and Cylinders  5.2.4. Volume and Surface Area of Cones
  6. Data Handling  6.1. Data Collection  6.1.1. Organizing Data  6.1.2. Frequency Distribution  6.2. Graphical Representation of Data  6.2.1. Bar Graphs  6.2.2. Double Bar Graphs  6.2.3. Pie Charts  6.2.4. Histograms  6.2.5. Line Graphs  6.3. Probability  6.3.1. Simple Events  6.3.2. Experimental Probability  6.3.3. Theoretical Probability
  7. Practical Geometry  7.1. Construction of Triangles  7.1.1. Constructing Triangles Given Side Lengths  7.1.2. Constructing Triangles Given Side and Angle  7.1.3. Constructing Right-Angled Triangles  7.2. Construction of Quadrilaterals  7.2.1. Quadrilaterals Given Side Lengths and Angles  7.2.2. Constructing Parallelograms and Rectangles

Grade 7 → Data Handling → Graphical Representation of Data ↓


Pie Charts


A pie chart is a type of graph used to represent data in a circular format. Each slice of a pie chart represents one data point and its size is proportional to the relative size of the data point compared to the entire data set. This makes pie charts a useful tool for visualizing data in an easy-to-understand way at a glance.

Structure of a pie chart

The basic structure of a pie chart involves a circle that is divided into segments (or slices). Each segment represents a range of data. The entire pie chart represents 100% of the data, with each slice representing a proportion of the whole data.

Total of all slices = 360°

Here's a simple example of the structure of a pie chart divided into four parts:

Creating a pie chart

To create a pie chart, you need to follow several steps that include collecting data, calculating the ratio, and creating the chart. Here's how you can do it:

Step 1: Collect the data

The first step in creating a pie chart is to gather all the data you need. This data can be anything from survey results to sales numbers. For example, let's say you conducted a survey about favorite fruits and you got the following responses:

  • Apples: 50
  • Bananas: 30
  • Cherries: 20
  • Grapes: 10

Step 2: Calculate the total

Next, add up all the data points to get a total. In the favorite fruit example, you would add up all the responses:

Total = 50 (Apples) + 30 (Bananas) + 20 (Cherries) + 10 (Grapes) = 110

Step 3: Calculate the angle for each slice

Each slice of the pie chart shows the degree of each category relative to the total. You calculate this by dividing each category number by the total, then multiplying it by 360 to convert it to degrees.

Using our fruit example:

  • Apple: (50 / 110) * 360 ≈ 163.63°
  • Bananas: (30 / 110) * 360 ≈ 98.18°
  • Cherry: (20 / 110) * 360 ≈ 65.45°
  • Grape: (10 / 110) * 360 ≈ 32.72°

Interpreting pie charts

When interpreting a pie chart, the size of each slice is important because it shows how much of the total each category represents. Larger slices represent larger proportions of the total, while smaller slices represent smaller proportions.

For example, a pie chart showing favorite fruits can help a store decide which fruits to stock more of. If apples represent the largest piece, it means apples are the most popular fruit.

Benefits of pie charts

Although pie charts have some limitations, they are beneficial in various scenarios due to their visual simplicity. Here are some of their benefits:

  • Simple Representation: Pie charts provide a clear and quick understanding of ratios.
  • Ease of interpretation: They allow easy comparison between segments.
  • Visually appealing: Pie charts are visually appealing and make data more interesting.

Disadvantages of pie chart

Despite their benefits, pie charts have their limitations. Here are some disadvantages:

  • Limited data points: Pie charts become cluttered and difficult to understand if there are too many categories.
  • Not suitable for exact comparisons: They are not suitable for making exact comparisons between different data sets.
  • Lack of space for values: Pie charts cannot clearly display numerical values on each slice.

Examples of pie charts

Let us check out some examples with detailed explanation:

Example 1: Favorite school subject

Suppose a class of students was asked about their favorite school subjects. The results are as follows:

  • Mathematics: 30 students
  • Science: 25 students
  • English: 20 students
  • Arts: 15 students
  • History: 10 students

Total number of students: 30 + 25 + 20 + 15 + 10 = 100

When these numbers are converted to degrees, the pie chart will look like this:

  • Mathematics: (30 / 100) * 360 = 108°
  • Science: (25 / 100) * 360 = 90°
  • English: (20 / 100) * 360 = 72°
  • Phase: (15 / 100) * 360 = 54°
  • History: (10 / 100) * 360 = 36°

Interactive tools

Today, many online tools and software allow you to create pie charts interactively. Excel, Google Sheets and many online chart-creating websites enable you to input data, choose the type of chart and customize the look of your pie chart.

Conclusion

Pie charts are a simple but powerful tool for visually displaying data. They help express proportional relationships within a data set, making it easy and quick to understand how individual parts relate to the whole. While pie charts are most effective with somewhat larger categories, they remain a staple in data visualization for their intuitive design and immediate impact.


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Pie Charts

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