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Mathematics · Number and place value
Maths: bar charts
A free preview from the Athena Learning Library — the same lesson registered students learn from.
In this lesson: Read values from a bar chart and use them to answer questions.
Before you start
Think back to a tally chart of your class's favourite fruit. Apples got 40 votes and Bananas got 10. How would you show those numbers as bars — and what would you check first on the axis before drawing anything?
Watch it happen
Watch a bar chart grow
An empty bar chart for favourite fruit. Start with the scale on the vertical axis: it goes up in 5s, so every gridline is worth 5. Reading the scale wrong is the classic bar-chart mistake.
Reading a bar: go across to the scale
To read the Apples bar, start at its top and travel straight across to the axis — never guess from where the bar stands. The dashed line lands on 40, so Apples = 40.
Your turn: sort the bars
Three of the favourite fruit bars, in a muddle. Swap neighbouring bars until they stand tallest first, shortest last.
Your target:
The idea
A bar chart uses bars whose heights show amounts. Always start with the scale on the axis: check what each square or step is worth before reading anything — on some charts each step is worth 2, 5 or 10, not 1.
To read a bar, run your eye from the top of the bar across (or down) to the axis and read the value carefully, estimating halfway points if the top lands between two marked values.
Questions often ask you to combine bars: 'altogether' means add the values, 'how many more' means subtract the smaller from the larger. Read every value first and write them down, then calculate.
Worked example
The bar chart shows the pets owned of a group of pupils. What is the difference between the number for Rabbits and the number for Hamsters?
- Read the scale first: the vertical axis goes up in 5s, so each big step is worth 5 — never guess a bar's height by eye.
- Read each bar by running your eye from its top straight across to the axis: Cats = 30, Hamsters = 5, Fish = 20, Rabbits = 40.
- Tallest bar Rabbits = 40; shortest bar Hamsters = 5; 40 − 5 = 35.
Answer: 35 pets — Tallest bar Rabbits = 40; shortest bar Hamsters = 5; 40 − 5 = 35.
Try one yourself
On this chart of pets owned, how many more pets does Dogs have than Birds?
Watch out
- Ignoring the scale and assuming every step is worth 1.
- Answering with just one bar's value when the question asks for two categories combined.
- Misreading a bar whose top falls between two marked lines.
Quick check
Try these on your own first — then reveal each answer.
1. On this chart, how many is the Cycle bar worth?
2. On this chart, how many children do Train and Car have between them?
Practise this concept
Reading is the first step — the concept sticks when your child answers questions on it. Registered students practise graded questions for this lesson, with instant marking and worked explanations, and the lesson is marked complete in their progress.