A batsman makes a score of 84 runs in the 21st inning and thus increases his average by 2 runs. His average after 21st inning is-

Answer: Option C

Let the average for 20 innings be x
$$\begin{array}{rl}& \therefore \frac{20x+84}{21}=x+2\\ & \Rightarrow 20x+84=21x+42\\ & \Rightarrow x=42\end{array}$$
∴ Average after 21st innings
= 42 + 2
= 44