Question

The mean of $x,x+2,x+4,x+6$ and $x+8$ is $11$, find the mean of the first three observations.

Answer 1

The mean of 5 observations $x,x+2,x+4,x+6,x+8$ is 11.

$Mean=\frac{Numberofobservations}{Totalobservations}$

$11=\frac{x+x+2+x+4+x+6+x+8}{5}$

$55=5x+20$

$5x=35$

$x=7$

Then, the first three terms will be,

$x=7$

$x+2=7+2$

$=9$

$x+4=7+4$

$=11$

The mean of first three terms is,

$Mean=\frac{7+9+11}{3}$

$Mean=\frac{27}{3}$

$Mean=9$