To determine the mode using a cumulative frequency graph, focus on identifying the steepest portion of the curve.

The mode is defined as the value that appears most frequently within a data set. When utilizing a cumulative frequency graph, also referred to as an ogive, the mode corresponds to the section of the graph exhibiting the steepest gradient. This steepest part signifies the interval with the highest frequency of data points.

To locate the mode on the graph, begin by plotting the cumulative frequency against the data values. The cumulative frequency represents the running total of frequencies up to each data point. As you plot these points and connect them with a smooth curve, pay close attention to where the curve ascends most sharply. This steep segment indicates the interval where the data values are most densely concentrated, thereby revealing the mode.

For instance, if you have a cumulative frequency graph illustrating the ages of students in a school, and you observe that the curve rises most sharply between the ages of $14$ and $15$, this interval is likely to contain the mode. To pinpoint the exact age within that range with greater precision, you can refer back to the original frequency table.

In summary, the cumulative frequency graph serves as a valuable tool for visualizing data distribution. By identifying the steepest part of the curve, you can quickly estimate the mode of the data set.