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Graphical Proportion

Graphical Proportion

Proportions can be shown graphically. A direct proportion will be shown as a straight line, passing through the origin (0,0).

Drawing a graph allows the proportion of different values to be obtained. By reading one scale, the graph can be used to determine the other proportion value.

Example 1

The exchange rate for Euros to British Pounds is €1 = £0.80. Draw a graph for the exchange rate for values from €0 to €180. Using the graph, determine the number of British Pounds that can be obtained for €140.

Plot the graph as shown.

Conversion of 144EUR to GBP

Then draw a line up from 140 Euros to meet the graph, then move along to read the amount in pounds from the vertical scale.

Answer: £112.00

Example 2

Using the graph, above, how many Euros would I receive for £100?

Read along from £100 to meet the graph, then drop down to read the amount in Euros from the horizontal scale.

Conversion of 100GBP to EUR

Answer: €125