Bar and column graphs

Leon jumps four metres—a good jump! Now he wants to compare how far he jumps, with some animals he knows are good at jumping. Here are columns, for animals and jump length, that create a table. We can also show the information like this: a graph consisting of different rectangles, or bars —a bar graph. The bars can either lie down, horizontally.. ..or stand up, vertically, as columns.

This type of bar graph is sometimes called a column graph. Now let's make a bar graph to show how long the animals and Leon jump. The bars should represent the length of the jump, so it works best for them to lie down. The graph should have two axis. Write a straight, horizontal line.

That axis will show how far the animals and Leon jump. At the end of the axis, write the unit we are using—metres. To make it clearer how long the jumps are, we make markings on the axis. What values should we use? Hmm?

Who jumps the furthest? The kangaroo jumps 13 metres. So we write 13 at the right end of the axis, and make a perpendicular line as a marker. Divide the axis with several small lines. One metre, two metres, three metres and so on.

Thirteen small lines with the same distance between each. Draw the second axis, a straight vertical line, starting from where the first axis is zero. Write the different animals and Leon, to the left of the axis, from the bottom to the top, equally spaced: frog, flea, kangaroo, Leon. Now, draw the bars. First the frog.

2.2 metres… That bar goes just beyond the 2-metre mark. Then the flea. 0.5 meters. The bar goes halfway to the first mark. The kangaroo can jump 13 metres.

We draw the bar all the way to the end of the horizontal axis. ..and Leon jumps four metres. Now we have turned the numbers into a picture of the different jump lengths.. ..and shown them in a horizontal bar graph. This information shows the average temperatures for two cities: Toronto, in Canada, and Montevideo, in Uruguay. We want to compare the average temperature in the different cities in different months. This is a bit difficult to do when we just look at the numbers, so let’s work on making this information into a graph.

The thermometer is vertical —we read temperature by height. Therefore, we choose a bar graph with standing bars. We use the horizontal axis for time. Write “month” at the end of the axis. Make 12 markings, one for each month.

January, February, and so on. Write the unit of measurement for temperature, degrees Celsius, on the vertical axis. The highest average temperature in any month is 27 degrees. So, 30 degrees can be our highest value. In order to fit 0 to 30 on the axis, we make a marking for every five degrees.

There are six marks: 5, 10, 15, and so on up to 30. First, we draw bars for Toronto: Since it is zero degrees in January and February, there are no bars. March, on the other hand, has an average temperature of four degrees. Draw a bar, that goes almost to the first marking. Draw the bars for the rest of the months.

Now, the city of Montevideo. We want to show clearly which bar belongs to which city.. So we colour the bars in different colours. We also make the bars narrower to fit between the markings on the horizontal axis. Toronto’s bars are red and Montevideo’s blue.

In January, the average temperature in Montevideo is 27 degrees. Draw the bar, for January. Draw the other months. 27, 24, 22 and so on. Now it is easier to compare the average temperature, between the cities.

And that is the very point of graphs. By making pictures from numbers, it is easier to understand what the numbers mean.