Question

The mean of 5 observation x,x+3,x+6,x+9,x+12 is 10.what is the mean of middle 3 observation?

Answer 1

Mean=10
(x+x+3+x+6+x+9+x+12)/5=10
(5x+30)=50
5x=50-30
5x=20
x=20/5
x=4
Mean of middle 3 observations =(x+3+x+6+x+9)/3
=(3x+18)/3
=(3×4+18)/3
=(12+18)/3
=30/3
=10

Answer 2

X=20
by x+x+3+x+9+x+12+x+6/5=10
x=50-30=20

x+3+x+6+x+9/3=20+3+20+6+20+9/3=78/3=26