# Unit 20 Section 3 : Line graphs

In this section we look at how to use line graphs.

## Example Question

Mr Smith recorded the temperature outside his classroom every hour during one school day.
His results are listed in the following table: He decided to plot a line graph to represent the data.
Line graphs are useful for showing how things change over time.

To plot the line graph, he drew some axes, plotted on a point for each item of data, then joined up the points: Mr Smith drew dashed lines on the graph to help him answer the two practice questions below.

See if you can answer the questions using the graph above.

Practice Questions
Work out the answer to each of these questions then click on the button marked to see whether you are correct.
(a) Estimate the temperature outside the classroom at 1030.

(b) Estimate the temperature at 1130

## Exercises

Work out the answers to the questions below and fill in the boxes. Click on the button to find out whether you have answered correctly. If you are right then will appear and you should move on to the next question. If appears then your answer is wrong. Click on to clear your original answer and have another go. If you can't work out the right answer then click on to see the answer.

 NOTE: In these questions you need to plot points and draw lines on grids. To plot a point, just click on the grid with your left mouse button. To draw a line, hold down the left mouse button at one end of the line and drag the pointer to the other end of the line. When you let go of the button the line will appear. If you make a mistake, press the delete key and the grid will be cleared.
Question 1
The outside temperature was recorded every hour during a school day. The results are given below:
(a) Draw a line graph for this data.

(b) Estimate the temperature at 1230       °C
(c) Estimate the temperature at 1530       °C
Question 2
The height of a plant was measured regularly after it had been transplanted, and the results are given below: (a) Draw a line graph to show how the height of the plant increased.

(b) Estimate the height of the plant after 10 days       cm
(c) Estimate the height of the plant after 18 days       cm
(d) Estimate the height of the plant after 13 days       cm
Question 3
A motorist on a long journey recorded the distances that he had travelled by various times: (a) Draw a line graph for this data.

(b) Estimate the distance travelled at 0830        miles
(c) Estimate the distance travelled at 1130        miles
(d) Estimate the distance travelled at 1300        miles
Question 4
Rachel keeps a record of the mass of her puppy as it grows. The records she has gathered are listed below: (a) Draw a line graph to display the above data.

(b) Estimate the mass of the puppy at 3 months       kg
(c) Estimate the mass of the puppy at 8 months       kg
(d) Estimate the mass of the puppy at 11 months       kg
Question 5
During a flood alert the depth of water in a river was measured several times.
The times and depths were recorded as shown below: (a) Draw a line graph to show the depth of the river.

(b) Estimate the depth of the river at 1030       m
(c) Estimate the depth of the river at 1800       m
(d) Estimate the depth of the river at 2300       m
Question 6
The depth of water in a harbour was recorded at various times during one day.
The data recorded is listed below: (a) Draw a line graph to show the depth of water in the harbour during the day.