Average of ten positive numbers is x. If each number is increased by 10%, then x :

Answer: Option D

Let 10 numbers be x1, x2, x3, . . . . . . . x10
According to question average of these 10 numbers is 10
$$\Rightarrow \frac{x1+x2+x3+....+x10}{10}=x$$
Now if each number is increased by 10%,
then new average, say y.
$$y=\frac{1.1x1+1.1x2+1.1x3+....+1.1x10}{10}$$
$$\Rightarrow y=1.1\times \frac{x1+x2+x3+....+x10}{10}$$
$$\begin{array}{rl}& \Rightarrow y=1.1x\\ & \Rightarrow y\text{is }10\%\text{increased}\end{array}$$