How to read a graph in a school question
Before describing a rising line, find out what is rising and how it was measured. A graph question may ask for a value, a comparison, a rate or an explanation. Those tasks need different answers, even when they use the same picture.
Read the labels before the shape
Read the title, both axis labels, their units and any key. Say the relationship aloud: “This graph shows temperature in degrees Celsius against time in minutes.” For multiple lines, identify which measurement or group each line represents before comparing them.
Check the spacing between numbered marks. Count the smaller divisions between two labels to find what each one represents. Look for an axis that starts above zero, a break in the scale or unequal intervals. A steep-looking line can result from the chosen scale, so use values when comparing changes.
Match the reading to the question
To find a value at a given time, start at that time on the horizontal axis, move to the plotted point or line, then read across to the vertical axis. Write the unit with your answer. For a bar chart, check the category beneath the bar and read its height against the numbered scale.
If the requested position lies between recorded points, decide whether the question allows an estimate from the line. Label an estimate as approximate and do not give more precision than the scale supports. Extending a line beyond the displayed data makes a prediction; it is a different step from reading a recorded value.
Work through a temperature graph
Imagine a line graph with these invented readings: at 0 minutes the temperature is 20 °C; at 2 minutes it is 30 °C; at 4 minutes it is 40 °C; at 6 minutes it is 40 °C. These numbers are a practice example, not results from a real experiment. The horizontal axis is time and the vertical axis is temperature.
The temperature at 4 minutes is 40 °C. From 0 to 4 minutes, the change is 40 − 20 = 20 °C. The average rate over that interval is 20 °C divided by 4 minutes, or 5 °C per minute. From 4 to 6 minutes, the change is zero. The highest temperature and the fastest rise answer different questions: a high point gives a value, while a rate uses a change over an interval.
A supported description is: “Temperature rose from 20 °C to 40 °C during the first 4 minutes, then remained at 40 °C through minute 6.” The flat section shows no recorded temperature change during that interval. It does not, by itself, establish why the temperature stayed constant or what happened after minute 6.
Attach evidence to each comparison
When comparing two lines, read both at the same horizontal position unless the question specifies different conditions. State the difference with its unit. When comparing rates, use change divided by interval length; a larger total change over a longer interval may still have a slower average rate.
For a trend question, describe the overall direction and any important change in pattern. Use this sentence frame: “Between [start] and [end], [quantity] changed from [value and unit] to [value and unit]. After [point], it [rose, fell or stayed constant], as shown by [values].” Choose the intervals that answer the question rather than listing every point.
Keep the explanation within the evidence
If the question asks why a pattern occurs, use the relevant idea from the lesson and connect it to the observed change. Separate that explanation from the values you read. A graph showing two quantities changing together does not alone prove that one caused the other; the surrounding method or information may be needed.
Before finishing, check the axis labels, units, interval and scope of your answer. If you described an increase, give the values that show it. If you calculated a rate, include the time interval. If you proposed a cause or predicted beyond the graph, check what additional evidence or assumption supports that step.
