Question

P.
(i) Following is the frequency distribution with unknown frequencies :
Class 20 – 30 30 – 40 40 – 50 50 – 60 Total
Frequency a 2a 3a a 70
Find the value of a and prepare a frequency distribution table for drawing a
frequency polygon. Draw a frequency polygon.​

Answer 1

The value of a is 10.

• Given frequencies a, 2a, 3a, a
• Given total is 70.

               a + 2a + 3a + a = 70

                      7a = 70

                       a = 10

Frequency distribution table:

               Class                   Frequency

              20 -30                        10

              30 -40                        20

              40 -50                        30

              50 -60                        10

               Total                          70

Frequency polygon:

• Frequency polygon is drawn by taking midpoints on x - axis and frequencies on y - axis.