Question

If the mean of x, x + 3, x + 5, x + 7 and x + 10 is 9 ,then what is the mean of last three observations?

Answer 1

(X+x+3+x+5+x+7+x+10)/5 = 9
5x+25=9
5x =9-25
X=(9-25)/5
X=4

Mean of last three observation is
(X+5+x+7+x+10)/3=
(4+5+4+7+4+10)/3 = 34/3
= 11.3