The idea in brief. Find the missing count or scale from the information given before completing the graph. A total for two equal bars must be shared between them. In the lesson. Last lesson, you added bars to find a total. Today, we use the information given to find a missing bar, and then we draw it. Find the missing count from the information given before completing the graph.
Lesson video, with the working
Recovering missing data and completing bars
4 min 43 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 seeds planted by three classes. The bar for Class 3B is missing. The three classes planted 75 seeds altogether. How many seeds did Class 3B plant?
3A and 3C: 20 + 30 = 50
3B: 75 − 50 = 25
Ans: 25 seeds
Example 1 of 2
The bar graph shows the number of cups of water drunk by three groups on Sports Day. The bar for Group A is missing. The three groups drank 65 cups altogether. How many cups did Group A drink?
B and C: 20 + 10 = 30
Group A: 65 − 30 = 35
Ans: 35 cups
Example 2 of 2
The bar graph shows the number of thank-you cards made by three classes. The bar for Class 3C is missing. Class 3C made 25 fewer cards than Class 3A. How many cards did Class 3C make?
3C: 40 − 25 = 15
Ans: 15 cards
How to solve it
Read what the question tells you: a total for all the classes, or how many more or fewer than a bar you can see.
A total is not the missing bar. First add the bars you can see: 20 plus 30 is 50.
Subtract the bars you can see from the total: 75 minus 50 is 25.
For more or fewer, start from the bar named: 40 minus 25 is 15.
Work out what one space stands for, then draw the missing bar up to that number.
Find the missing count from the information given before completing the graph.
Practice questions with worked solutions
Question 1 is free to try. The other 6 open in the free trial, each with its solution film.
Question 1 of 7 · Basic · free to tryThe horizontal graph shows the number of cups filled at three water…The horizontal graph shows the…
The horizontal graph shows the number of cups filled at three water stations. There were 84 cups altogether. Station A’s bar is missing. How many cups were filled at Station A?
How do you find the missing bar in P3 bar graph missing data questions?
Here part of a bar graph is missing, and the question gives a total or a comparison instead.
What your child learns here
Here part of a bar graph is missing, and the question gives a total or a comparison instead. Your child works out the missing count and completes the graph. This applies the Primary 3 outcomes on interpreting bar graphs and using different scales, with addition and subtraction.
Add the bars that can be seen, then subtract their sum from the total to find the missing bar.
For 'more than' or 'fewer than', start from the bar named and add or subtract.
Recover the scale when the axis numbers are missing, using a bar whose value is known.
Share a total between equal bars, such as two bars of the same height for one day.
Draw the missing bar to the correct height on the scale.
Does the answer make sense?
A missing bar found from a total must be smaller than that total, and your child can check that all the bars together add back to it exactly. If two bars are unknown and nothing links them except their total, the honest answer is that it is not possible to tell.
How to practise these questions
The Basic question practises finding a missing value by subtracting the known bars from the total. The Intermediate questions add completing the bar on the graph once its value is found. The Challenge questions give the missing bars through equal numbers on one day, or ask whether the information is enough to find a value at all. If a missing bar question stalls, watch the solution film for it and try once more later from Revision.
Questions parents ask
How does my child work out a missing value on a bar graph? Use what the question gives. With a total, add the bars that can be seen and subtract their sum from the total. With 'more than' or 'fewer than', start from the bar named and add or subtract.
Is completing a bar graph in the P3 syllabus? The P3 syllabus lists reading and interpreting data from bar graphs, and using different scales on the axis. Finding and drawing a missing bar applies both outcomes.
What if the axis on the bar graph has no numbers? Use a bar whose value is given. Count its spaces and divide its value by that number to find what one space stands for.
