Reading a Line Graph

A line graph shows how something changes over time. Time runs across the bottom, the amount runs up the side, and each dot is one measurement. Here a puppy is weighed once a month: at month 1 it weighs 3 kilograms, at month 2 it weighs 5, and so on.

Across: the month. Up: the weight in kilograms.

To read a value, find the time along the bottom, go straight up to the dot, then across to the side. To find a change, read two dots and subtract the earlier value from the later one. From month 2 to month 5 the puppy went from 5 to 9 kilograms: 9 - 5, so it gained 4.

The shape tells the story before any arithmetic. When a line joins the dots in order, a steep climb between two dots is a fast gain, a flat stretch is no change, and a drop is a loss. Here every step goes up, so the puppy gained weight every month, fastest where the dots climb by 2.