Question

The mean of 5 observation is 15 if the mean of first three observation is 14 and the mean of last three observation is 17 find the third obsevation

Answer 1

Let, 5 observations are a, b, c, d, e
So, (a+b+c+d+e) /5 =15
a+b+c+d+e=75
Now,(a+b+c)/3=14
a+b+c=42
( c+d+e) /3=17
c+d+e=51
42+51=a+b+c+d+e+c
93-75=c
c=18
Third observation =18