52. The mean of the following frequency distribution is 43.75 :
Class
0-10
10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 90 - 100
re
8
4
Frequency
20
45
64
32
8
f
2
2
ai
Find the missing frequency f.
pic
Answers
Answer:
178
Step-by-step explanation:
i used step deviation method to find
Solution :-
Class Fi Xi FiXi
0-10 8 5 40
10-20 4 15 60
20-30 20 25 500
30-40 45 35 1575
40-50 64 45 2880
50-60 32 55 1760
60-70 f 65 65f
70-80 8 75 600
80-90 2 85 170
90-100 2 95 190
⅀Fi=185+f ⅀FiXi=7775+65f
we know that,
- Mean = ⅀FiXi / ⅀Fi
so,
→ (7775 + 65f) /(185 + f) = 43.75
→ 7775 + 65f = 8093.75 + 43.75f
→ 65f - 43.75f = 8093.75 - 7775
→ 21.25f = 318.75
→ f = (318.75/21.25)
→ f = 15 .(Ans.)
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