Question

If the mean of 5 observations x, x+2, x+4, x+6 and x+8 is 11, the mean of the last 3 observations is

Answer 1

Mean=x+x+2+x+4+x+6+x+8/5
11. =5x+20/5
11x5. =5x+20
55. =5x+20
55-20=5x
35=5x
35/5=x
x=7

Mean of last 3 observations=x+4+x+6+x+8/3


=7+4+7+6+7+8/3

=11+13+15/3

=39/3

=13

therefore mean of last 3 observations is 13