2 3 1
7
Find the average of 65,5--4- and 7
5' 4' 5 10
1
1
1
2.
(c) 4.
80
(d) 7
80
8080
Find the average of 20 20
(a) 5-1
(b) 6
10
Answers
Answered by
3
Answer:
Correct option is
D
8,12
Class
Frequency(f)
ClassMark (x)
fx
0-20
5
10
50
20-40
f
1
30
30f
1
40-60
10
50
500
60-80
f
2
70
70f
2
80-100
7
90
630
100-120
8
110
880
Total
30+f
1
+f
2
2060+30f
1
+70f
2
Given 30+f
1
+f
2
=50
=>f
1
+f
2
=20 -- (1)
Given, Mean =
∑f
∑fx
=62.8
=>
30+f
1
+f
2
2060+30f
1
+70f
2
=62.8
=>2060+30f
1
+70f
2
=1884+62.8f
1
+62.8f
2
32.8f
1
−7.2f
2
=176
=> 8.2f
1
−1.8f
2
=44
=> 4.1f
1
−0.9f
2
=22 -- (2)
Solving both equations 1, 2, we get
f
1
=8,f
2
=12
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