5 Line graphs

Line graphs are a very useful way to spot patterns or trends over time. You will have looked at how to plot and interpret single line graphs from single data sources in Everyday maths 1. Now you will be looking at line graphs that show the results of two data sources.

The example below shows the monthly foreign exchange rate of £1 against the US dollar and the euro. You can clearly see how the pound was dropping in value against the euro and US dollar up to October 2016. Now that you understand how line graphs can be used and why they are useful, next you’ll learn how to draw and interpret them.

Figure 19 Monthly foreign exchange rate of £1 against the US dollar and the euro from May 2016 to January 2018.

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A line graph. The horizontal axis is labelled ‘Year’ and has 11 data points from ‘May-16’ to ‘Jan-18’. The vertical axis is labelled ‘Units of currency’ and has 11 data points from 1.0 to 1.50.

Euro data points are:

31 May 16 – 1.2846

31 Jul 16 – 1.1884

30 Sep 16 – 1.1722

30 Nov 16 – 1.1533

31 Jan 17 – 1.1613

31 Mar 17 – 1.1548

31 May 17 – 1.1696

31 Jul 17 – 1.1281

30 Sep 17 – 1.1186

30 Nov 17 – 1.1259

31 Jan 18 – 1.1331

US Dollar data points are:

31 May 16 – 1.4518

31 Jul 16 – 1.3141

30 Sep 16 1.3142

30 Nov 16 – 1.2431

31 Jan 17 – 1.2351

31 Mar 17 – 1.2348

31 May 17 – 1.2933

31 Jul 17 – 1.2994

30 Sep 17 – 1.3324

30 Nov 17 – 1.3219

31 Jan 18 – 1.3832

Figure 19 Monthly foreign exchange rate of £1 against the US dollar and the euro from May 2016 to January 2018.

Now that you understand how useful line graphs can be and how they can be used, next you’ll learn how to draw and interpret them.