Graphs: Are You Plotting Something?

Contributor: Jamie Hagler. Lesson ID: 13776

Whether you are actually plotting something sneaky or doing your math homework, learn how to utilize bar graphs, line graphs, and histograms in your everyday life!

categories

Algebra I, Modeling

subject
Math
learning style
Visual
personality style
Golden Retriever
Grade Level
High School (9-12)
Lesson Type
Skill Sharpener

Lesson Plan - Get It!

Audio:

For the past few months, you have been trying to save money. Somehow, though, you have not been able to do so.

  • Where could all your money be going?
  • Is something costing you more than usual?
  • How can you find out?

Oh no! Maybe your phone bill has been increasing.

  • Or has it been decreasing?

You can graph your phone bill charges on bar graphs, line graphs, and histograms. This will help you visually see if your bills are increasing or decreasing over time.

Each type of graph is different.

A bar graph presents data with rectangular bars with heights equal to the values that they represent.

For example, this bar graph represents Eden's cell phone bill over several months:

bar graph

Each bar represents the bill amount for that month. The first J is for January, and the bar goes up to $60:

January bar graph

Then, the F is for February, and the bar goes to $50, and so on for each month:

February bar graph

  • Does the amount of Eden's cell phone bills increase or decrease?

If you look at the top of each graph and then look at the next one, you can see if the amount of the cell phone bill increased.

Looking at the bar graph, we see that the charge decreased, then increased, and decreased again.

Over the last three months, we see a pattern that shows that the amount of Eden's cell phone bill charges has decreased.

A line graph is used to show information that changes over time. We plot line graphs using several points connected by straight lines.

This line graph represents the same cell phone bill as in the bar graph:

line graph

Just like the bar graph, J is for January, and the bill is at $60. But this time, it is a dot at $60:

January line graph

The F is for February, and the dot is at $50, and so on for the rest of the months:

February line graph

Looking at the line graph, we see that the charge decreased, then increased, and decreased again.

Over the last three months, we see a pattern that shows that the amount of the cell phone bill charges has decreased, just as the bar graph showed.

A histogram uses bars of different heights. Each bar groups numbers into ranges.

We can represent Eden's cell phone bills with a histogram; however, it will not show us whether her cell phone bill is increasing or decreasing.

  • Why not?

The histogram represents the same cell phone bills as the bar graph and line graph:

histogram

The bar graph and line graph represented each month individually. A histogram shows the data differently, in groups.

There are no rectangles above $10, $20, or $30. This is because no month's bill was that amount.

However, the rectangle above $40 goes to 1 because one month had a bill that was $40:

histogram to 40

The rectangle above $50 goes to 2 because there were two months when the cell phone bills were $50. The remaining sections of the histogram represent the other charges for bills:

histogram to 50

The histogram represents the cell phone bill charges over several months, but it is not a good representation to determine if the bills are increasing or decreasing.

  • Ready to put all this into practice?

Then head over to the Got It? section!

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