Single Line Graphs — Prelims Strategy

Prelims Strategy

Copy the relevant points into a table before performing more than one calculation. Write the elapsed time between observations explicitly, especially when the graph skips hours or years. Use signed differences for rises and falls and retain the measurement unit when converting to a rate.

Read the stem for the distinction between maximum value, greatest increase and steepest absolute change. For a missing intermediate value, look for an explicit linear interpolation condition; do not treat a connecting line as proof of a measured observation. When a value repeats, check whether the question asks for every matching time or only the earliest one.

For journey or storage graphs, interpret the vertical variable before attaching a physical explanation. Final minus initial gives net change, not necessarily total distance travelled or gross inflow. Finish with a telescoping check: the sum of signed interval changes must match the endpoint difference. This check is quick and identifies many subtraction or interval-omission errors without repeating the whole solution.