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Home  >>  CBSE XI  >>  Math  >>  Statistics
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Find first 10 multiples of 3

$\begin{array}{1 1}(A)\;74.25\\(B)\;56\\(C)\;12\\(D)\;53\end{array} $

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1 Answer

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  • First 10 multiples of 3 are $3,6,9,12,15,18,21,24,27,30$
Step 1:
$x_i =3 , \qquad x_i^2=9$
$x_i =6 , \qquad x_i^2=36$
$x_i =9 , \qquad x_i^2=81$
$x_i =12 , \qquad x_i^2=144$
$x_i =15 , \qquad x_i^2=225$
$x_i =18 , \qquad x_i^2=324$
$x_i =21 , \qquad x_i^2=441$
$x_i =24 , \qquad x_i^2=576$
$x_i =27 , \qquad x_i^2=729$
$x_i =30 , \qquad x_i^2=900$
Total of $x_i=165$
Total of $x_i^2=3465$
Step 2:
Mean $\bar{x}= \large\frac{\sum x}{n}$
$\qquad = \large\frac{165}{10}$$=16.5$
Step 3:
Variance $=\large\frac{\sum x_i^2}{n} - \bigg(\large\frac{\sum x_i}{n} \bigg)^2$
$\qquad= \large\frac{3465}{10} =\bigg( \large\frac{165}{10}\bigg )^2$
$\qquad = 346.5 -(16.5)^2$
$\qquad= 346.5 -272.25$
$\qquad= 74.25$
Hence A is the correct answer.
answered Jun 27, 2014 by meena.p
 
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