Question

= 1-21=2
18. Case Study II
Students Studying in Class Room
In a mathematic class, a teacher explain the
concept for determine the mean by defining
the formula =
Σfx,
Efi
7
Further, a teacher give one example for
explaining the above concepts.
The marks obtained by 30 students of
class X of a certain school in a mathematics
paper consisting of 100 marks are
presented in table below
Class interval
10-25
25-40
40-55
55-70
70-85
85-100
Number of
Students
2
3
7
6
6
6
(a) Find the average marks obtained by
the students.
(i) 61
(ii) 62
(iii) 63
(iv) 64​

Answer 1

Given : The marks obtained by 30 students of   cla ss X of a certain school in a mathematics   paper consisting of 100 marks  

To Find : the average marks obtained

(i)  61

(ii) 62

(iii) 63

(iv) 64​

Solution:

Cla ss interval     f         Mean   d= (mean-62.5)/15      d*f

10-25                  2        17.5         -3                              -6

25-40                 3        32.5        -2                             -6

40-55                 7        47.5        -1                               -7

55-70                 6        62.5        0                               0

70-85                 6        77.5          1                               6

85-100               6        92.5          2                             12

                         30                                                       -1

Mean = 62.5  + 15 x (-1)/30

= 62.5 - 0.5

= 62

Learn More:

The average marks obtained by Raghav in 12 tests is 24. Zubeida

brainly.in/question/9930646

 a cla ss of 45 stu de nt s , bo ys and gi rls are in the  of 5 : 4  

brainly.in/question/7989701