Question

If the mean of a set of observations $x_1,x_2,......,x_{10}$ is 20, then the mean of $x_1+4,x_2+8,x_3+12,....,x_{10}+40$ is

• A. $34$
• B. $42$
• C. $38$
• D. $40$

Answer 1

Answer: (B)

$42$

Given $\because \frac{x_1+x_2+.......+x_{10}}{10}=20$
$\Rightarrow x_1+x_2+....+x_{10}=200$
Required mean $=\frac{(x_1+4)+(x_2+8)+.....+(x_{10}+40)}{10}$
$=\frac{(x_1+x_2+.....+x_{10})}{10}+\frac{4(1+2+....+10)}{10}$
$=20+22=42$