P6 Mathematics - Term II

Topic 6: Data Handling

Lesson 3: Line Graphs - Construction and Interpretation

Duration: 45 minutes

Today's Learning Objectives for Line Graphs

By the end of this lesson, you will be able to:

• Understand what a line graph is
• Identify and label the axes correctly
• Plot points using coordinates
• Draw and interpret a line graph over time

Reviewing the Graph Types So Far

What we've learned so far:

• Frequency tables - Show exact numbers in rows and columns
• Pie charts - Show parts of a whole as slices

Each graph type has its own special purpose!

What is a Line Graph?

A line graph shows how data changes over time or across different conditions

Key features:

• Two axes (horizontal and vertical lines)
• Points plotted where data occurs
• Points connected with straight lines
• Shows trends (going up, down, or staying the same)

When to Use Line Graphs

Line graphs are best for:

• Showing change over time
• Tracking trends and patterns
• Temperature through the day
• Attendance over a week
• Rainfall each month
• Plant growth over weeks

Different from pie charts: Line graphs show change, not parts of a whole

Understanding the Two Graph Axes

Horizontal axis (x-axis):

• Bottom line, left to right
• Usually shows time or what changes

Vertical axis (y-axis):

• Side line, going up and down
• Shows what we measure

An Important Rule About the Axes

Remember this rule:

Horizontal axis = What changes (time, categories)
Vertical axis = What we measure (numbers, amounts)

Example:

• Horizontal: Days of the week
• Vertical: Temperature in degrees Celsius

Creating Scales for Your Axes

The scale is how we number our axes

For vertical axis:

• Start at zero or lowest number
• Count up evenly (by 1s, 5s, 10s, etc.)
• Space marks equally
• Go high enough for your highest number

Example scale: 0, 5, 10, 15, 20, 25, 30

Worked Example: A Temperature Graph

Data: Daily temperature for one week

Let's turn this into a line graph!

Step 1: Draw the Axes

Draw an L-shape:

• Horizontal line for days
• Vertical line for temperature
• Use a ruler for straight lines
• Make axes large enough (about 10 cm each)

Label each axis clearly!

Step 2: Create the Scales

Horizontal axis: Mark five equal spaces for Mon, Tue, Wed, Thu, Fri

Vertical axis:

• Lowest temperature = 15°C
• Highest temperature = 22°C
• Scale: 0, 5, 10, 15, 20, 25
• Mark evenly with ruler

Step 3: Plot the First Point

Monday = 15°C

How to plot:

1. Find Monday on horizontal axis
2. Go straight up to 15 on vertical axis
3. Make a clear mark (dot or small X)

This is called plotting a point!

Step 4: Plot All Points

Continue for each day:

• Tuesday (18°C)
• Wednesday (20°C)
• Thursday (22°C)
• Friday (19°C)

Check each point carefully for accuracy!

Step 5: Connect the Points

Use your ruler to:

• Draw straight lines connecting the points
• Go from left to right (Mon → Tue → Wed → Thu → Fri)
• Connect each point to the next point
• Keep lines straight and neat

Now you can see the temperature trend!

Step 6: Add a Title

Every graph needs a title!

Write at the top:
"Temperature in Kampala - One Week"

or

"Daily Temperature Monday to Friday"

The title tells readers what the graph shows

Practice Reading Our Line Graph

What can we learn from our graph?

• Which day was hottest? (Thursday - 22°C)
• Which day was coolest? (Monday - 15°C)
• When did temperature increase most? (Mon to Thu)
• Overall trend? (Temperature mostly increased)

The line shows the story of the data!

Understanding Trends in a Graph

A trend is the general pattern or direction

• Increasing - line goes up
• Decreasing - line goes down
• Stable - line stays flat

Our graph: increasing Mon-Thu, then a small decrease Fri

Practice: Graphing School Attendance Data

Data: Learners present each day

Draw this line graph in your exercise book!

Important Tips for Graphing Success

Remember:

• Use a ruler for ALL straight lines ✓
• Space your scales evenly ✓
• Plot points carefully ✓
• Label both axes clearly ✓
• Add a descriptive title ✓
• Check your work ✓

Take your time - accuracy matters!

Comparing the Three Graph Types

Use the right graph for your data!

Real-Life Uses of Line Graphs

Where are line graphs used?

• Weather reports (temperature, rainfall)
• Business (sales trends, stock prices)
• Health (patient temperature, weight tracking)
• Education (test score progress)
• Agriculture (crop growth, harvest yields)
• Sports (performance statistics)

Common Line Graph Mistakes to Avoid

Watch out for these errors:

• Uneven spacing on axes
• Forgetting to label axes
• Not using a ruler
• Wrong scale (too small or too large)
• Forgetting the title
• Curved lines instead of straight

Careful work prevents mistakes! ✓

Summary of Today's Key Points

• Line graphs show change over time
• Two axes: horizontal (time), vertical (measurement)
• Create even scales on both axes
• Plot points, connect with straight lines
• Trends: increasing, decreasing, or stable
• Always label axes and add titles

Looking Ahead to Mean and Median

Tomorrow's lesson:
We will learn to calculate mean, median, and mode - important statistics!

What these are:

• Mean = Average
• Median = Middle value
• Mode = Most common value

Bring: Exercise book, pen, pencil

Homework: Collect Your Own Changing Data

Collect one of these (5 days or 5 people):

• Daily temperature at the same time
• Vehicles passing by each day
• Your family members' ages

Then create a frequency table for it

Homework: Draw and Describe Your Graph

Draw a complete line graph with:

• Labeled axes and appropriate scale
• All points plotted accurately
• Straight lines connecting points
• A clear title

Write three sentences about what your graph shows

Expected time: 25-30 minutes