Lesson Guide
Explanation
A column graph is right when you are comparing separate things — how many students like each sport, say. A line graph is right when one thing is changing over time. Here the temperature rises through the morning, peaks in the middle of the afternoon, and drops in the evening. The line joins the readings because the temperature really did pass through every value in between; it did not jump from one reading to the next.
Your Turn
Which would you use for the heights of five different trees? Check: a column graph, because they are five separate things, not one thing changing.
Watch Out
Only join points with a line when the in-between values are real. Joining favourite sports would be meaningless.
Explanation
To read a value, find the time along the bottom, travel straight up until you hit the line, then straight across to the number on the side. At 3pm the line sits level with 28, so the temperature was 28 degrees. Use a ruler or your finger to keep the two lines straight — sliding by one gridline is the easiest mistake in the topic, and it is completely avoidable.
Your Turn
What was the temperature at 9am? Check: 18 degrees.
Watch Out
Check what each gridline is worth before you read anything. Here each one is 10 degrees, not 1.
Explanation
You can read a line graph without looking at a single number, just from its shape. A line going up means the value is increasing. A flat line means it is not changing at all — between hours 2 and 3 here the distance stayed at 30 km, so whoever it was had stopped. A line going down means decreasing. And steepness matters: the steeper the line, the faster the change is happening. Being able to describe the shape in words is half of what these questions ask for.
Your Turn
Between which hours was the change fastest? Look for the steepest section. Check: between hours 0 and 1, and again between 4 and 5.
Watch Out
A flat line does not mean zero. It means no CHANGE — the value is holding steady at whatever it was.
Explanation
A timeline is a number line where the numbers are years. Events are marked at the right point along it, and the crucial thing is the spacing: a bigger gap means more time passed. That is what makes a timeline better than a simple list — you can see at a glance that the stretch from the First Fleet to the gold rush was far longer than from the gold rush to Federation. To work out how long between two events, subtract the years.
Your Turn
How many years from Federation in 1901 to the Sydney Olympics in 2000? Check: 2000 minus 1901 = 99 years.
Watch Out
Events evenly spaced on the page are NOT evenly spaced in time unless the scale says so. Read the years, not the gaps.
Explanation
Two things to watch. First, the vertical axis does not always start at zero, and starting it high makes a tiny change look dramatic — that is a favourite trick in advertising, so always check the scale before believing a shape. Second, only the marked points are actual measurements. The line between them is an estimate; nobody stood outside at half past one taking a reading. It is usually a reasonable guess, but if a question asks how confident you are, that is the answer it is looking for.
Your Turn
A graph of house prices starts its vertical axis at 900 thousand instead of 0. Why might someone do that? Check: to make a small rise look like a huge one.
Watch Out
Never judge a line graph by its shape alone. Look at what the numbers on the side actually say.
📌 Key Points — this lesson in a nutshell
- Line graphs show one thing changing over time; column graphs compare separate things.
- To read a value: up from the bottom axis, then across to the side.
- Shape tells the story: up = increasing, flat = no change, down = decreasing.
- Steeper means faster change.
- A timeline is a number line of years — the spacing shows how much time passed.
- Always check the scale, and remember the line between points is a guess.
Step 1: Introduction
Step 1 of 5
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