Question

Q33. Find mean marks
Marks
No. of students
0 and above 80
10 and above 77
20 and above 72
30 and above 65
40 and above 55
50 and above 43
60 and above 28.
70 and above 16
80 and above 10
90 and above 8
100 and above 0
​

Answer 1

Similarly, the number of students getting marks between 10 and 20 is 77-72= 5 and so on. Thus, we obtain the following frequency distribution.

Marks Number of students

0-10 3

10-20 5

20-30 7

30-40 10

40-50 12

50-60 15

60-70 12

70-80 6

80-90 2

90-100 8

Now, we compute mean arithmetic mean by taking 55 as the assumed mean.

Computative of Mean

Marks(x i ) Mid-value (f i ) Frequency u ii10x ii−55 f i u i

0-10 5 3 -5 -15

10-20 15 5 -4 -20

20-30 25 7 -3 -21

30-40 35 10 -2 -20

40-50 45 12 -1 -20

50-60 55 15 0 0

60-70 65 12 1 12

70-80 75 6 2 12

80-90 85 2 3 6

90-100 95 8 4 32

Total ∑fi =80 ∑f iiu i = -26

We have,

N= sumf i =80,∑f iiu i =−26, A= 55 and h= 10

∴ X =A+h[ N1∑fi ui]⇒ X =A+h[ N1 ∑f iiu i ]⇒

X=55+10× 80−26

=55−3.25=51.75Marks.

Answer 2

Answer:
mmean marks = 51.75
Step-by-step explanation: