Question

Following table shows a frequency distribution for the speed of cars passing through at a particular spot on a high way:

Class interval (km/h)	Frequency
30 – 40	3
40 – 50	6
50 – 60	25
60 – 70	65
70 – 80	50
80 – 90	28
90 – 100	14

Draw the frequency polygon representing the above data without drawing the histogram.

Answer 1

First we obtain in the class marks (mid-marks) of the given table as:

Class-marks = `("Lower limit" + "Upper limit")/2`

Since, the new table is shown below:

Class interval	Class marks	Frequency
30 – 40	35	3
40 – 50	45	6
50 – 60	55	25
60 – 70	65	65
70 – 80	75	50
80 – 90	85	28
90 – 100	95	14

Now, let’s draw a frequency polygon by plotting the class marks along the x-axis and the frequency along y-axis.

Also, plotting all the points as B(35, 3), C(45, 6), (D(55, 25), E(65, 65), F(75, 50), G(85, 28) and H(95, 14). 

Then join all these point line segment, shown below: