notes
The information in a frequency table can be presented in various ways. We have studied a histogram. A frequency polygon is another way of presentation.
Let us study two methods of drawing a frequency polygon.
(1) With the help of a histogram (2) Without the help of a histogram.
(1) We shall use the histogram in figure to learn the method of drawing a frequency polygon.
1. Mark the mid  point of upper side of each rectangle in the histogram.
2. Assume that a rectangle of zero height exists preceeding the first rectangle and mark its mid  point. Similarly, assume a rectangle succeeding the last rectangle and mark its mid point.
3. Join all mid  points in order by line segments.
4. The closed figure so obtained is the frequency polygon.
(2) Observe the following table. It shows how the coordinates of points are decided to draw a frequency polygon, without drawing a histogram.
The points corresponding to the coordinates in the fifth column are plotted. Joining them in order by line segments, we get a frequency polygon. The polygon is shown in figure . Observe it.
Related QuestionsVIEW ALL [7]
Draw a frequency polygon from the information given in the following table.
Age of blood donar (Years)  No. of blood donars 
Less than 20  0 
Less than 25  30 
75Less than 30  75 
165Less than 35  127 
Less than 40  165 
Less than 45  185 
Less than 50  197 
In a handloom factory different workers take different periods of time to weave a saree. The number of workers and their required periods are given below. Present the information by a frequency polygon.
No. of days

8  10  10  12  12  14  14  16  16  18  18  20 
No. of workers  5  16  30  40  35  14 
The time required for students to do a science experiment and the number of students is shown in the following grouped frequency distribution table. Show the information by a histogram and also by a frequency polygon.
Time required for
experiment (minutes) 
20  22  22  24  24  26  26  28  28  30  30  32 
No. of students  8  16  22  18  14  12 
Draw a frequency polygon for the following grouped frequency distribution table.
Age of the donor
(Yrs.) 
20  24  25  29  30  34  35  39  40  44  45  49 
No. of blood doners  38  46  35  24  15  12 
The following table shows the average rainfall in 150 towns. Show the information by a frequency polygon.
Average rainfall (cm)

0  20  20  40  40  60  60  80  80  100 
No. of towns  14  12  36  48  40 
The maximum bowing speed (km/hour) or 33 players at a cricket coaching centre is given below:
Bowling Speed(km/hour)  85100  100115  115130  130145 
Numbers of players  9  11  8  5 
find the modal bowling speed of players.
The time required for some students to complete a science experiment and the number of students is shown in the following grouped frequency distribution table. Draw the frequency polygon with the help of histogram using given information:
Time required for experiment (minutes)  Number of Students 
20  22  6 
22  24  14 
24  26  20 
26  28  16 
28  30  12 
30  32  10 