If the mean of 5 observations \(x, x+2, x+4, x+6\) and \(x+8\) is 11, then value of x:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 7
The mean is the sum of the observations divided by their number.
Sum \(=x+(x+2)+(x+4)+(x+6)+(x+8)=5x+20\)
\(\displaystyle\frac{5x+20}{5}=11\)
\(5x+20=55\)
\(x=7\)
Shortcut: The observations are equally spaced, so their mean is the middle one:
\(x+4=11\), so \(x=7\)