What will be the Last Three Mean Observation? If

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

  1. 11
  2. 13
  3. 15
  4. 17
101hostings Default Asked on 26th July 2015 in Maths.
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1 Answer(s)

Answer: (2) 13
Explanation:-
Given-
5 observations are X, X + 2, X + 4, X + 6  and X + 8.
Mean = 11
Formula-
Mean of the observation = Sum of the observation /number of the observation
Then, (X + X + 2 + X + 4 + X + 6 + X + 8)/5 = 11
5 X + 20  = 11 x 5
5 X = 55- 20
5 X = 35
X = 35/5
X = 7
Now, the value of the last three observations X + 4 = 7 + 4 = 11,  X + 6 = 7 + 6 = 13   & X + 8 = 7 + 8 = 15
Then, the mean of the last three observations =  (11 + 13 + 15)/3
= 39/3
= 13
Hence, the answer is (2) 13.

Anurag Mishra Professor Answered on 26th July 2015.
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