Graphs show data, the information you collect, as a picture. In Grade 1 you sorted data into groups (Data in Three Groups). Picture graphs and bar graphs make groups easy to compare.
Why it works
In a picture graph, each picture is one thing, so you count pictures. In a bar graph, the height of a bar is the number: read straight across from the top of the bar to the numbers on the side. Every grid line counts, even the ones without a number.
Worked example: Read a bar
How many children have fish?
- The Fish bar stops one line above 6.
- Each line is 1 more, so it is 7.
Answer: 7 children
Worked example: Compare
How many more children have dogs than cats?
- Dogs: 9. Cats: 5.
- $9 - 5 = 4$.
Answer: 4 more children
Worked example: Total
How many children answered?
- Add every bar: $9 + 5 + 7 + 2 = 23$.
Answer: 23 children
Key idea
Picture graph: count the pictures. Bar graph: read across from the top of the bar. Then add or subtract to answer questions.
Common mistake
Reading a bar that ends between two numbered lines as the lower number. The Fish bar ends one line above 6, so it shows 7, not 6. Check: count the lines up from the last number you can see.
Grown-up tip: Make a tally of something at home, like the colors of cars passing by, and draw a bar graph together.