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NCERT Class XI Mathematics - Statistics - Solutions

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Question : 15
Total: 34
First 10 multiples of 3
Solution:  
Here xi = 3, 6, 9, 12, 15, 18, 21, 24, 27, 30
Σxi = 3 + 6 + 9 + 12 + 15 + 18 + 21 + 24 + 27 + 30 = 165
n = 10
∴ Mean (
−
x
) =
165
10
 = 16.5
Σxi2 =
(3)2+(6)2+(9)2+(12)2 + (15)2+(18)2+(21)2+(24)2+(27)2+(30)2

∴ Variance (σ2) =
nΣxi2−(Σxi)2
n2
=
10×3465−(165)2
(10)2
 =
34650−27225
100
 =
7425
100
 = 74.25
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