Question

Mean of x,x+2,x+4,x+6and x+8is 11.the mean of first three observations will be;

Answer 1

Given observations are : X , X + 2 , X + 4 , X + 6 and X + 8.


Mean of observations = Sum of observations/ Number of observations.



11 = ( X + X + 2 + X + 4 + X + 6 + X + 8 ) / 5




5X + 20 = 11 × 5


5X + 20 = 55


5X = ( 55 - 20 )



5X = 35


X = 7


First observation = X = 7


Second Observation = X + 2 = 9


And,

Third observation = X + 4 = 11.



Mean of First three observations = ( 7 + 9 + 11 ) / 3 = 27/3 = 9



Hence,

Mean of first three observations will be 9.