A student was asked to arithmetic mean of numbers 3,11,7,9,15,13,8,19,17,21,14 and x . He found mean

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A student was asked to find the arithmetic mean of the numbers $3,11,7,9,15,13,8,19,17,21,14$ and $x$. He found the mean to be $12 .$ What should be the number in place of $x ?$

A

$3$

B

$7$

C

$17$

D

$31$

Solution

Given $12$ numbers and mean to be $12.$

Sum of $12$ numbers $=12 \times 12=144$

$x=144-(3+11+7+9+15+13+8+19+17+21+14)=144-137=7$

Standard 13

Quantitative Aptitude

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