Question

10. Calculate the mean of the distribution, given below, using the short cut method :
11-20
Marks
21-30
31-40
41-50
51-60
61-70
71-80
5 - 90
2.
6
No. of students
10
8
12
9
7
4
[2​

Answer 1

Answer:

Marks Class−Mark

x

i

No.ofstudents

f

i

f

i

x

i

10.5−20.5 15.5 2 31

20.5−30.5 25.5 6 153

30.5−40.5 35.5 10 355

40.5−50.5 45.5 12 546

50.5−60.5 55.5 9 499.5

60.5−70.5 65.5 7 458.5

70.5−80.5 75.5 4 302

∑f

i

=50 ∑f

i

x

i

=2345

⇒ Mean(

x

)=

∑f

i

∑f

i

x

i

=

50

2345

=46.9