Question

find the value of a and prepare a frequency distribution table for drawing a frequency polygon. draw a frequency polygon.
class :-20-30,30-40,40-50,50-60,
Frequency :-a, 2a, 3a, a, total 70​

Answer 1

The value of a is 10

Given frequencies are a, 2a, 3a, a

Total of frequencies = 70

a + 2a + 3a + a = 70

                 7a = 70

                   a = 10

    Class             Midpoint            Frequency

   20 - 30                 25                        10

   30 - 40                 35                        20

   40 - 50                 45                        30

   50 - 60                 55                        10

                                                          N = 70

Frequency Polygon:

• Take midpoints on X - axis
• Take frequencies on Y - axis
• Use scale to join the points.