Question

Find the average. Marks of the students from the following data. Marks below. 10 20 30 40 50 60 70 80 no. Of students. 15 35 60 84 96 127 198 250

Answer 1

0-10 15
10-20 20
20-30 25
30-40 24
40-50 12
50-60 31
60-70 71
70-80 52
Total
Mid value 5,15,25,35 ,45,55,65,75
Average =5*15+15*20+25*25+35*24+45*12+55*31+65*71+75*52 divided by 250
=75+300+625+840+540 +1705+4615+ 3900 /250
12600/250=50.4

Answer 2

Given:

Marks below. 10 20 30 40 50 60 70 80 no. Of students. 15 35 60 84 96 127 198 250

To Find:

The Average of the above data

Solution:

In order to find the average, we will arrange the data in the following way:

Class  Frequency  Mid Value

                 (Fi)             (Xi)

0-10             15              5

10-20          20             15

20-30         25             25

30-40         24              35

40-50          12              45

50-60          31              55

60-70           71              65

70-80           52             75

We know that,

Average = ∑FiXi / ∑Fi

So,

Average = {(5x15) + (15x20) + (25x25) + (35x24) + (45x12) + (55x31) +(65x71) + (75x52)} / 250

               = 75 + 300 + 625 + 840 + 540 + 1705 + 4615 + 3900 / 250

               = 12600 / 250 = 50.4

Hence, the average is 50.4