Introducing line graphs

Line Graphs

• Line graphs visually represent data trends over time. 
• They are useful for showing how one variable changes in relation to another.

Horizontal Axis

• Definition: The horizontal axis, located at the bottom, progresses from left to right.
• Example: In the provided graph, the horizontal axis is labeled as "Time," indicating that time increases as we move along the line.
• Illustration: An arrow on the graph signifies the time's progression along the horizontal axis.

Vertical Axis

• Information Provided: The vertical axis indicates the temperature in degrees Celsius.
• Starting Point: It commences at 0°C.
• Increment: The scale progresses in increments of 2°C (e.g., 2, 4, 6...).
• Clarification: Although the labels increase by 2s, temperatures like 7°C or 9°C can still be measured on the graph, even if not explicitly labeled.

Examples

Example 1: Take a look at the graph again.
When was it 10°C?
Sol:

It was 10°C at 1pm.
Did you notice another time of the day when the temperature was 10°C?
Keep travelling across the line once you've reached 1pm and you will see that it was also 10°C at 2.30pm.
This means there are two times when the temperature was 10°C.

Example 2: When was the temperature 16°C?
This time we know the temperature but not the time.

• First we slide up the vertical axis to 16°C and travel across to meet the line.
• Then we travel straight down to reach the horizontal axis which reads 4pm.

It was 16°C at 4pm.