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  • The mean of 25 observations is 36. Out of these observations if the mean of first 13 observations is 32 and that of the last 13 observations is 40, the 13th observation is : (A) 23 (B) 36 (C) 38 (D) 40

The mean of 25 observations is 36. Out of these observations if the mean of first 13 observations is 32 and that of the last 13 observations is 40, the 13th observation is :

\\(A) 23 \\ (B) 36\\ (C) 38 \\ (D) 40

Answers (1)

Answer : B

\text {Mean}=\frac{\text {Sum of observations}}{\text {No.of observation}}

The mean of 25 observations is 36.

36=\frac{\text {sum of 25 observations}}{25}

\Rightarrow Sum of 25 observations =900.

For first 13 observations, mean is given as 32

32=\frac{\text {sum of 13 observations}}{13}

\Rightarrow Sum of last 13 observations

=40 \times 13 = 520

Now, 13th observation = sum of 13 observation+sum of last 13 observation-sum of 25 observations.

\Rightarrow 13th observation =416+520-900=36

The value of 13th observation is 36

Therefore option (B) is correct.

Posted by

infoexpert23

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