In this section, we are going to be looking at questions where we need to interpret the graph that we are given to answer some questions. We are going to be looking at two examples.

**Example 1**

The graph below shows the height of a tide from 9:00 to 15:00.

Answer the following questions:

Part A asks us to find the maximum height of the tide. The maximum height of the tide will be the point on the graph that has the highest

- Part A: what is the maximum height of the tide and when does it occur?
- Part B: for how many hours is the height of the tide 5 metres or above?

**Part A**Part A asks us to find the maximum height of the tide. The maximum height of the tide will be the point on the graph that has the highest

*y*value. I have labelled this point on the graph below.The maximum height of the tide is 7.5 metres and the time when this occurs is 12:30.

Part B asks us to find the number of hours that the tide is 5 metres or higher. We answer this question by finding a height of 5 on the

**Part B**Part B asks us to find the number of hours that the tide is 5 metres or higher. We answer this question by finding a height of 5 on the

*y*axis and drawing a horizontal line across.The first time when the height of the tide is 5 metres or above is at 11:00. The height of the tide remains 5 metres or above until 15:00 when the height of the tide becomes 5 metres again. We can work out the number of hours by completing the following calculation.

Therefore, the tide is 5 metre or above for 4 hours.

**Example 2**

The graph below shows the how temperature changes over a 24-hour period.

Answer the following questions based on the above graph:

Part A asks us to work out the range of temperature, which we are able to do by taking the lowest temperature from the highest temperature. The highest temperature will be the highest point on the curve, and the lowest temperature will be the lowest point on the curve. I have labelled these points on the curve below:

- Part A: what is the range of temperatures during the 24-hour period?
- Part B: for how many hours was the temperature 23°C or below?

**Part A**Part A asks us to work out the range of temperature, which we are able to do by taking the lowest temperature from the highest temperature. The highest temperature will be the highest point on the curve, and the lowest temperature will be the lowest point on the curve. I have labelled these points on the curve below:

The highest temperature is 28°C and the lowest temperature is 12°C. Therefore, the working out for the range is:

The range of temperatures is 16°C.

Part B asks us to find the number of hours that the temperature is 23°C or lower. We answer this question by finding 23°C on the

**Part B**Part B asks us to find the number of hours that the temperature is 23°C or lower. We answer this question by finding 23°C on the

*y*axis and drawing a horizontal line across.From the above graph, we can see that there are two sections of the graph whereby the temperature is 23°C or less. The first section is 2 hours and the second section is 13 hours (24 – 11). Therefore, the total number of hours that the temperature is 23°C or less is 15 hours (2 + 13).