Grade 6 Mathematics Data Handling – Bar Graphs Notes

Mathematics — Data Handling

Subtopic: Bar Graphs (Age 11 — Kenyan context)

Learning goals:

• Know parts of a bar graph (title, axes, scale, labels, bars).
• Draw a simple bar graph from a frequency table or tally.
• Read information and answer questions from a bar graph.

Key words

• Bar graph: A picture that uses bars to show numbers.
• Frequency: How many times something happens.
• Axis (plural: axes): The lines (horizontal and vertical) on a graph.
• Scale: The numbers used on the vertical axis to show size.
• Label: The name for each axis or each bar.

Parts of a bar graph

1. Title: Tells what the graph is about.
2. Horizontal axis (x-axis): Shows the categories (e.g., types of transport).
3. Vertical axis (y-axis): Shows the numbers (frequency).
4. Bars: Rectangles whose heights (or lengths) show the size of each category.
5. Scale: Choose numbers that cover the largest frequency and are easy to count (1, 2, 5, 10 etc.).

Step-by-step: How to draw a vertical bar graph

1. Collect data and make a tally table.
2. Make a frequency table showing each category and its number.
3. Decide a suitable scale for the vertical axis (the highest frequency should fit on the graph).
4. Draw the axes, add labels and a title.
5. Draw bars of equal width with equal spaces between them. Height must match the frequency.
6. Write the numbers on top of or inside each bar (optional but useful).

Example (Kenyan school context)

A teacher asked 30 pupils: "How do you come to school?" The answers are:

Questions (read the graph)

1. Which is the most common way pupils come to school?
2. How many pupils come by matatu?
3. How many more pupils walk than go by bicycle?
4. What is the total number of pupils who use motor vehicles (Matatu, Bus, Car)?
5. If 2 more pupils start coming by bus, what will be the new number for Bus?

Answers

1. Walk — it has the tallest bar (12 pupils).
2. 8 pupils come by matatu.
3. 12 (walk) − 5 (bicycle) = 7 more pupils walk than ride bicycles.
4. Matatu 8 + Bus 3 + Car 2 = 13 pupils use motor vehicles.
5. 3 + 2 = 5 pupils (Bus will have 5 pupils).

Tips and common mistakes

• Always write the title and label both axes — without them the graph is unclear.
• Use a scale that covers the largest frequency. If numbers are large, use steps of 2, 5 or 10.
• Do not start the vertical axis at a number other than 0 unless stated — this can mislead readers.
• Give equal width to bars and equal spacing between bars.
• Use colours or patterns if many categories are similar — this makes the graph easier to read.

Practice (try these)

1. A school class recorded favourite fruits: Mango 6, Banana 10, Orange 4, Avocado 5. Make a frequency table and draw a bar graph.
2. From a bar graph showing number of books read by pupils in a month (Tom 7, Amina 5, Peter 3, Joy 6): Which pupil read the least? How many read more than 5 books?

These notes are suitable for learners around 11 years old (Standard 5/6). Use simple tools: squared paper, ruler and colour pens to practise drawing neat bar graphs.