The cumulative frequencies can be visually represented using the Ogive graph. Here, the class boundaries are given along the X-axis, and the cumulative frequencies are provided along the Y-axis. 

For example, consider a frequency table of customers who bought cameras of different price ranges. Note that the class boundaries that separate the classes without gaps are listed in the table.

To find out the number of customers who purchased the cameras that cost less than 80 dollars, a cumulative frequency for the class less than 80 is calculated. It is given by the sum of the frequencies of the current class and all the preceding classes. Similarly, the remaining cumulative frequencies are calculated.

In the graph, each point connected by a continuous line represents the cumulative frequency below the respective class boundary. For instance, ten customers bought cameras that cost less than 79.5 dollars, while 18 bought the ones costing less than 99.5.