It quite often happens in a GCSE exam that you will be expected to deal with graphs that show real life situations.

In this activity, we will deal exclusively with reciprocal graphs.

**What is a reciprocal graph?**

A reciprocal graph is any graph that has the form **f(x) = a/x or 1/x**

This will give the graph that looks something like this:

**Example: **

Water is poured out of a beaker.

The volume left in the beaker is plotted against time.

**Describe the relationship between the time and the volume of water left in the beaker.**

All this question is asking for is a statement about whether the volume is **increasing or decreasing.**

For this example, we can say that as time increases, the volume of water decreases.

** At what time is there 2 litres left in the beaker?**

** How much water is left in the beaker after 1 minute?**

Both of these can be done by using the graph line to convert between the two values:

Reading from the graph, there are 2 litres left after** 2 minutes** and after 1 minute, there are approximately **3.5 litres left.**

Time for some questions now.