1) If the mean of 5 observations x, x + 2, x + 4, x + 6 and x + 8 is 11, then the mean of the last three observations is : A) 11 B) 13 C) 15 D) 17 Answer: Option BExplanation:We have [x+(x+2)+(x+4)+(x+6)+(x+8)5]=115x+20 = 55x= 7So the numbers are 7,9,11,13,15Required mean = 11+13+153=393=13