Question

C. The electricity bills (in Rs.) of 40 houses in a locality are given below:
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
Electricity
Bills in Rs.
No. of
houses.
2.
6
5
8
5
7
3
4
Find the mean and median of the above frequency distribution.
[4]​

Answer 1

Given : The electricity bills (in Rs.) of 40 houses in a locality are given  

To Find : mean and median of the above frequency distribution.

Solution:

Class         Mean   d=(Mean- 85)/10      f    cf          d.f

50-60           55              -3                     2    2           -6

60-70          65              -2                     6     8            -12

70-80          75               -1                     5      13         -5

80-90          85               0                     8      21          0

90-100          95              1                      5     26          5

100-110          105             2                    7      33         14

110-120          115               3                    3     36          9

120-130         125             4                    4      30         16

                                                              40                 21

Mean  = 85  + 10 * ( 21)/40

= 85 + 5.25

= 90.25

Median =  80 + 10 * (20 - 13)/8

= 80 + 8.75

= 88,75

Mode =  80 + 10 * (8 - 5)/(8 - 5 + 8 - 5)

= 80  + 5

= 85

Mode = 85

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