A bar graph for big numbers cannot mark every one. So it steps by 2, 5, or 10.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
Read the numbers, not the height
A bar reaching the third mark on a scale of 5 is 15, not 3.
Bars between marks
A bar halfway between 10 and 20 is 15. Work out what half a step is worth.
Check the scale before any reading
A bar graph might go up in 1s, 2s, 5s or 10s. On a scale of 5, a bar reaching the third line means 15, not 3. Before you read a single bar, look at two adjacent numbers on the axis and work out the step.
Bars that stop between lines
On a scale of 10, a bar halfway between 20 and 30 means 25. You are reading a number line, so the same "count the spaces, not the marks" thinking applies. Estimate carefully rather than rounding to the nearest labelled line.
Why scales are used at all
If a category had 300 items, a scale of 1 would need a graph three hundred squares tall. Scales let large data fit on a page. The cost is that every reading needs a small calculation, which is a fair trade.
Step 2: Try It Yourself
Tap and try it out.
Apples
Balls
Fish
Key: each symbol stands for 5.
There are 85 in all.
Fish has the most. It has 25 more than Balls.
Step 3: Watch an Example
One step at a time.
Watch Leo Read a Scale
A bar graph steps by 5 and a bar reaches the fourth mark.
- Step 1
He checks the scale before reading the bar.
Step 4: Your Turn
Practice makes it stick.
The Class Survey
Problem 1 of 2
A scale steps by 10. A bar reaches the fourth mark. What value is it?
Halfway Up
Problem 2 of 2
On a scale stepping by 10, a bar sits halfway between 20 and 30. What is it?
Read the Scale
1 of 3
A scale of 5, bar at the sixth mark. What value?
2 of 3
A scale of 2, bar at the seventh mark. What value?
3 of 3
A scale of 5. Bars at 30 and 15. How many more is the first?
Step 5: Quick Check
Show what you know.
Question 1 of 2
A scale of 5, bar at the seventh mark. What value?
Question 2 of 2
Why check the scale first?
What You Learned
- A scaled bar graph steps by more than one.
- Read the numbers on the axis, not the number of marks.
- Work out what half a step is worth for bars in between.