Reading Charts and Graphs
A primary math lesson on reading charts and graphs: understand pictograms, bar charts and tally marks, read the key and axis, and answer data questions with a quiz.
Key takeaways
- A chart shows information, called data, in a picture so it is easy to read.
- A tally chart counts in groups of five with a line crossed through.
- A pictogram uses pictures, and a key tells you what each picture is worth.
- A bar chart uses bars; taller bars mean bigger numbers.
- Always read the title, the labels, and the key before answering questions.
What Is Data?
Every day we collect information. How many sunny days were there this week? What is everyone's favourite fruit? How many cars drove past the school? This information is called data.
Data is helpful, but a big list of numbers can be hard to read. So we put data into a picture called a chart or a graph. A good chart lets you see the answer at a glance, without counting everything again. Let's learn three kinds: tally charts, pictograms, and bar charts.
Tally Charts
A tally chart is a quick way to count things as they happen. Each time you see something, you draw one line. To make counting easy, we count in groups of five.
For the first four, you draw four straight lines:
| | | |
For the fifth, you draw a line across the other four, like a little gate:
ε (four lines with one crossed through)
This makes groups of 5, which are super fast to count: 5, 10, 15... just like skip counting by 5s!
Here is a tally chart of pets in a class:
| Pet | Tally | Total | |||
|---|---|---|---|---|---|
| Dog | ε ε | 10 | |||
| Cat | ε | 8 | |||
| Fish | 3 |
To find a total, count the groups of five and add the leftovers. For cats: one group of 5, plus 3 more, equals 8.
Pictograms
A pictogram uses pictures instead of lines. Each picture stands for a number of things. The most important part is the key, which tells you what one picture is worth.
The key is the secret code. Always read it first!
Imagine a pictogram of apples eaten this week, where the key says:
π = 2 apples
| Day | Apples |
|---|---|
| Monday | ππ |
| Tuesday | π |
| Wednesday | πππ |
Now we use the key to work out the real numbers:
- Monday has 2 pictures.
2 Γ 2 = 4 apples - Tuesday has 1 picture.
1 Γ 2 = 2 apples - Wednesday has 3 pictures.
3 Γ 2 = 6 apples
See how the key changes everything? If you ignored it and just counted pictures, you would get the wrong answer! Using the key is really just multiplication in disguise.
Sometimes a pictogram shows half a picture to mean half the value. If one whole apple is 2, then half an apple means 1.
Bar Charts
A bar chart uses bars to show amounts. The taller the bar, the bigger the number. Bar charts make it easy to compare things side by side.
A bar chart has parts you need to read:
- A title at the top tells you what the chart is about.
- The bottom labels (the horizontal axis) tell you the groups, like "cats" and "dogs."
- The side numbers (the vertical axis) tell you the amounts, like 0, 1, 2, 3...
Imagine a bar chart titled "Favourite Animals." The bars reach these heights:
| Animal | Bar reaches |
|---|---|
| Cats | 6 |
| Dogs | 4 |
| Rabbits | 3 |
| Birds | 2 |
To read it, follow the top of each bar across to the side numbers. The cat bar is the tallest, reaching 6, so cats are the most popular. The bird bar is the shortest at 2, so birds are the least popular.
Answering Questions About Charts
Charts let us answer all kinds of questions. Using the animal chart above:
- Which is most popular? The tallest bar wins: cats (6).
- Which is least popular? The shortest bar: birds (2).
- How many more cats than dogs? Subtract:
6 β 4 = 2. Two more cats. - How many animals altogether? Add them all:
6 + 4 + 3 + 2 = 15animals.
Notice how reading charts uses your addition and subtraction skills to compare and total things up.
A Golden Rule
Before you answer any chart question, always do these three steps:
- Read the title. What is this chart about?
- Read the labels. What do the rows, bars, or columns mean?
- Read the key or the numbers. How much is each picture or each line of the axis worth?
If you skip these steps, it is easy to make mistakes, like forgetting that one picture might mean 2 things instead of 1.
Why Charts Matter
Grown-ups use charts everywhere: weather forecasts, sports scores, sales at shops, and results in science. Being able to read a chart means you can quickly understand information and make good choices. It is a skill you will use for the rest of your life.
Try It Yourself
Become a data detective with these activities:
- Make a tally. For one day, make a tally each time you hear someone say "thank you." At the end, count your groups of five. What is the total?
- Build a pictogram. Ask 5 friends or family for their favourite colour. Draw a smiley face for each person next to each colour. Add a key: 1 face = 1 person.
- Read a real chart. Find a weather chart on TV or in a paper. Which day will be warmest? How do you know?
- Bar chart questions. Using the "Favourite Animals" table above, work out: how many more rabbits than birds? (Answer: 3 β 2 = 1.)
Now you can read tally charts, pictograms, and bar charts like a true data expert. Charts turn numbers into pictures, and you know how to read them! π
Quick quiz
Test yourself and earn XP
In a tally chart, how do you write the number 5?
Five is shown as four lines with the fifth crossed through, making a 'gate' of 5.
In a pictogram, the key says one apple picture = 2 apples. What do 3 apple pictures mean?
Each picture is worth 2, so 3 pictures = 3 x 2 = 6 apples.
On a bar chart, what does a taller bar mean?
The taller the bar, the bigger the amount it stands for.
What should you read FIRST on any chart?
Reading the title, labels, and key first tells you what the chart is about.
A bar chart shows 6 cats and 4 dogs. How many more cats than dogs?
6 cats minus 4 dogs = 2 more cats.
FAQ
People often use the words to mean the same thing: a picture that shows information, called data. A bar chart, a pictogram, and a tally chart are all ways of showing data so it is easy to read.
A key tells you how much each picture is worth. For example, the key might say one star = 2 children. So 4 stars would mean 8 children.
Look at the title to see the topic, read the labels along the bottom and side, then check how tall each bar is. The number it reaches on the side axis tells you the amount.
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