Explanation
Class
Frequency (f)
Class Mark (x)
fx
0-10
5
25
10-20
x
15
15x
20-30
375
30-40
16
35
560
40-50
6
45
270
Total
42 + x
1230 + 15x
Given, Mean $$ = \cfrac { \sum { fx } }{ \sum { f} } = 27 $$
$$ => \cfrac {1230 + 15x}{42 + x} = 27 $$
$$ => 1230 + 15x = 1134 + 27x $$
$$ 96 = 12x $$
$$ x = 8 $$
Frequency(f)
0-5
2
2.5
5-10
4
7.5
30
10-15
8
12.5
100
15-20
17.5
105
20-25
10
22.5
225
465
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