Early Math · Grade 2
Picture Graphs, Bar Graphs and Line Plots
Quick answer
A line plot shows measurements: a number line of whole units with one dot for each object measured, stacked where lengths repeat. A picture graph and a bar graph show how many are in each of a few groups — one picture per item, or a bar that reaches the count on a scale going up by ones from 0. Graphs answer questions about totals and differences: add the groups to put them together, and subtract to compare them.
What you'll learn
- Measure several objects and show the lengths on a line plot
- Draw a picture graph and a bar graph for up to four groups
- Solve put-together, take-apart and compare problems from a bar graph
Measure and make a line plot
A class measured pencils to the nearest inch. Here are the lengths:
A line plot shows them. Draw a number line of inches. Put one dot above the length of each pencil. When two pencils have the same length, stack the dots.
The tallest stack is at . More pencils are inches long than any other length.
Picture graphs
A class voted for their favorite fruit. A picture graph shows one picture for each vote.
Count the dots in each row: apples, bananas, grapes and pears.
Bar graphs
A bar graph shows the same votes with bars. Each bar reaches its count on the scale.
The scale starts at and goes up by ones, so you can read each count.
Why the scale starts at 0
The length of a bar should match its count. A bar for should be twice as long as a bar for .
That only works when every bar starts at . If the scale started at , the bar for would look tiny next to the bar for . Starting at 0 keeps the bars fair, so the picture tells the truth.
Worked examples
Common mistakes
Practice problems
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Here are the lengths of crayons, in centimeters: , , , , , . How many dots go above on a line plot?
Answer
Full solution
Three crayons are centimeters long, so three dots stack above .
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Use this line plot of shoe lengths. What length is most common?
Shoe lengths in inches Answer
inches
Full solution
The tallest stack, dots, is above .
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In the shoe line plot, how many shoes were measured?
Answer
Full solution
Count every dot: .
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In the shoe line plot, what is the difference between the longest and shortest shoe?
Answer
inches
Full solution
The longest is inches and the shortest is . .
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Use this bar graph of pets. How many kids have a cat?
Our pets Answer
Full solution
The cats bar ends at on the scale.
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In the pet graph, how many more dogs than cats are there?
Answer
Full solution
more dogs.
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In the pet graph, how many pets are there in all?
Answer
Full solution
. Try first, then , so .
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In the pet graph, fish and birds together are how many?
Answer
Full solution
.
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Make a picture graph: kids like red, like blue and like green. How many pictures go in the green row?
Answer
Full solution
A picture graph shows one picture for each vote, and green got votes.
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Kai reads the pencil line plot and says the longest pencil is inches, because has the most dots. What went wrong?
Hint
What does the height of a stack tell you?
Answer
The most dots means the most common length. The longest pencil is inches.
Full solution
A stack’s height counts how many pencils have that length. Where the stack sits on the line gives the length.
The dot farthest to the right is at , so the longest pencil is inches.
Frequently asked questions
What is a line plot?
A number line with a dot for each measurement. When several things have the same length, their dots stack up above that number.
What is the difference between a picture graph and a bar graph?
A picture graph shows one picture for each item. A bar graph shows a bar that reaches up to the count on a number scale.
Why does a bar graph's scale start at 0?
So each bar's length matches its count. A scale that starts higher makes small differences look big.
How do I find how many more are in one group?
Subtract the smaller count from the bigger one. 6 grapes and 3 bananas means 6 − 3 = 3 more grapes.
How many groups can a second-grade graph have?
Up to four, such as four favorite fruits or four kinds of pets.
Standards alignment
This lesson covers the following Common Core State Standards for Mathematics.
- CCSS.MATH.CONTENT.2.MD.D.9Measurement and DataGenerate measurement data by measuring lengths of several objects to the nearest whole unit, or by making repeated measurements of the same object. Show the measurements by making a line plot, where the horizontal scale is marked off in whole-number units.
- CCSS.MATH.CONTENT.2.MD.D.10Measurement and DataDraw a picture graph and a bar graph (with single-unit scale) to represent a data set with up to four categories. Solve simple put-together, take-apart, and compare problems using information presented in a bar graph.