The idea, step by step
Read both axes
A line graph pairs each time with a measurement. Read the horizontal time first, then the point's height on the vertical scale. Check the unit: a height of 8 centimetres is not a temperature of 8 degrees.
The line helps us follow a pattern between recorded points. A value read between points is an estimate; it was not necessarily measured then.
Describe the change
Find the change between two readings by subtracting the earlier value from the later value. Look at the measured numbers rather than only saying the line is steep. A horizontal section shows no measured change.
When drawing, use even spacing for time and an even number scale. Plot each pair, then join neighbouring times in order. Include a title and units.
| Day | Height (cm) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 5 |
| 4 | 8 |
| 5 | 9 |
A common trap
A higher point means a greater increase.
Instead: A point shows a value. An increase is the difference between two values.
See the thinking
Read and compare
How tall was the seedling on day 4? How much did it grow from day 3 to day 4?
- Day 4 has height 8 cm.
- Day 3 has height 5 cm.
- 8 − 5 = 3.
A falling section
A container holds 12 litres at 9 am, 9 litres at 10 am and 9 litres at 11 am. Describe its line graph.
- Plot time horizontally and volume in litres vertically.
- The graph falls from 12 to 9 between 9 and 10 am.
- It is horizontal from 10 to 11 am, because both readings are 9.
Check your understanding
What is the seedling's growth from day 1 to day 5?
Show answer
7 cm.
The final height is 9 cm and the first is 2 cm: 9 − 2 = 7 cm.
Your turn
6 questions · 10 marks · Work at your own pace.
Read the questions online
- Read the seedling's height on day 2.1 mark
- How much did the seedling grow from day 2 to day 3?1 mark
One seedling measured at the same time each day Day Height (cm) 1 2 2 4 3 5 4 8 5 9 - Between which neighbouring days was its largest increase?2 marks
One seedling measured at the same time each day Day Height (cm) 1 2 2 4 3 5 4 8 5 9 - Readings are 5, 5, 7 at 1, 2, 3 pm. Describe the first section of a line graph.1 mark
- Draw a line graph for times 0, 1, 2, 3 seconds and distances 0, 2, 4, 6 metres.3 marks
- A graph joins day 1 height 2 cm to day 2 height 4 cm. Is the halfway height of 3 cm a measured reading?2 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Read the seedling's height on day 2.1 mark
Locate day 2, then read the height of its point.
4 cm. - How much did the seedling grow from day 2 to day 3?1 mark
One seedling measured at the same time each day Day Height (cm) 1 2 2 4 3 5 4 8 5 9 5 − 4 = 1 cm.
1 cm. - Between which neighbouring days was its largest increase?2 marks
One seedling measured at the same time each day Day Height (cm) 1 2 2 4 3 5 4 8 5 9 The increases are 2, 1, 3 and 1 cm.
3 cm is the greatest.
Days 3 and 4. - Readings are 5, 5, 7 at 1, 2, 3 pm. Describe the first section of a line graph.1 mark
Both readings are 5.
Horizontal: the reading stays at 5 between 1 and 2 pm. - Draw a line graph for times 0, 1, 2, 3 seconds and distances 0, 2, 4, 6 metres.3 marks
Use equal steps on each axis.
The distance increases by 2 metres each second, so the plotted points form a straight line.
Plot (0,0), (1,2), (2,4), (3,6) and join in time order. Label Time (seconds), Distance (metres), and a suitable title. - A graph joins day 1 height 2 cm to day 2 height 4 cm. Is the halfway height of 3 cm a measured reading?2 marks
Only the day 1 and day 2 measurements were supplied.
The seedling may not have grown at a constant rate between them.
No. It is an estimate between two recorded readings.
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum 2026
Data types/validation; mode; suitable displays; line graphs; statistical investigations.
Official curriculum source ↗