The idea in brief. Read the legend and compare a complete total with a complete total. Read the legend. Compare totals with totals, not one bar with two. In the lesson. Last lesson, you read a bar graph using its scale. Today, we use the legend to find totals, and then we compare them. Read the legend and compare a complete total with a complete total.
Lesson video, with the working
Comparing and combining paired bars
4 min 22 s
The film teaches 3 questions in turn. Each question shows first; its working is written as the film explains it.
The bar graph shows the number of storybooks and comics borrowed from the class library on three days. How many more storybooks than comics were borrowed altogether?
Storybooks: 20 + 10 + 30 = 60
Comics: 25 + 15 + 5 = 45
60 − 45 = 15
Ans: 15 storybooks
Example 1 of 2
The bar graph shows the number of apples and pears sold at three stalls at a school fun fair. How many pieces of fruit did Stall B sell altogether?
Stall B: 15 + 25 = 40
Ans: 40 pieces of fruit
Example 2 of 2
The bar graph shows the number of paper stars and paper boats made by three teams. How many more items did Team A make than Team C?
Team A: 25 + 20 = 45
Team C: 30 + 5 = 35
45 − 35 = 10
Ans: 10 items
How to solve it
Read the legend. It tells you which colour is which kind.
Decide what the question needs. Altogether means every day or stall, so find the total of each kind first.
Read each bar from the scale and add: storybooks 20 plus 10 plus 30 is 60.
Do the same for the other kind: comics 25 plus 15 plus 5 is 45.
For how many more, compare a complete total with a complete total: 60 minus 45 is 15.
Read the legend and compare a complete total with a complete total.
Practice questions with worked solutions
Question 1 is free to try. The other 6 open in the free trial, each with its solution film.
How do you compare totals in P3 double bar graph questions?
Some Primary 3 bar graphs show two bars side by side for each day, stall or team, with a legend saying which colour is which.
What your child learns here
Some Primary 3 bar graphs show two bars side by side for each day, stall or team, with a legend saying which colour is which. This page applies the syllabus outcome on reading and interpreting data from bar graphs to totals and comparisons that use both bars.
Use the legend to tell the two kinds apart.
Decide whether the question needs one kind across every group, or both kinds for one group.
Add the bars that make each total before comparing.
Answer 'how many more' with the difference of two complete totals.
Turn counts into money by pricing each kind separately when they cost different amounts.
Does the answer make sense?
A group's total cannot be smaller than either of its two bars, and a 'how many more' answer must be smaller than the larger of the two amounts compared. When every voucher, flower or fan is worth $2 or more, your child should find the money is at least double the number of items counted.
How to practise these questions
The Basic question practises reading both bars in a pair. The Intermediate questions add comparing pairs, such as how many more of one item a group collected. The Challenge questions ask your child to combine and compare across groups before giving one answer. When a paired bar question is stuck, play its solution film together and return to it later from Revision.
Questions parents ask
What is a double bar graph in Primary 3? It is a bar graph with two bars for each group, such as two kinds of fruit at each stall. A legend shows which colour stands for which kind. The P3 syllabus covers it under reading and interpreting data from bar graphs.
How do I help my child read the legend on a bar graph? Ask them to read the legend aloud first and name each colour. Then ask them to point at one bar and say both which group it belongs to and which kind it shows.
Does my child need to add the bars before comparing? When the question compares groups or kinds as a whole, yes. Each side of the comparison should be a complete total, made from every bar it includes.
