Question

If mean of 5 observations x , x+2 , x+4 , x+6 , x+8 is 12. Find the mean of first three observations.

Answer 1

Answer

Mean=sum of all observations/no. Of observation

Therefore

12=(5x+20)/5

5x=60-20

X=8

First observation = 8

2nd=10

3rd=12

Mean=(8+10+12)/3

Mean=30/3

=10

Answer 2

GIVEN :
5 observations - x , x+2 , x+4 , x+6 , x+8
Mean of 5 observations - 12

TO FIND :
Mean of first 3 observations = ?

SOLUTION :

Total sum Obserations = Mean
_________________
No of Observation

x + x + 2 + x + 6 + x + 8 + x + 4 = 12
_______________________
5
5x + 20 = 12
______
5
5(x + 4) = 12
_______
5
x + 4 = 12
x = 12 - 4
x = 8

Now, substitute the value of x in every observation .
so x + 2 = 8 + 2 = 10 .......1)
X + 4 = 8 + 4 = 12 .........2)
X + 6 = 8 + 6 = 14..........3)
X + 8 = 8 + 8 = 16 .............4)

Now the mean of 3 awards

Mean = 8+ 10 + 12
_________________
3
= 30
____
3
= 10

=
hence the mean of 3 observations is 10 .



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