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1. Ajit has a certain average for 9 innings. In the tenth innings, he scores 100 runs thereby increasing his average by 8 runs. His new average is:

A. 20

B. 21

C. 28

D. 32

Solution:

Let Ajit's average be x for 9 innings. So, Ajit scored 9x run in 9 innings.
In the 10^th inning, he scored 100 runs then average became (x+8). And he scored (x + 8) × 10 runs in 10 innings.
Now,

\begin{aligned} \Rightarrow 9 x + 100 = 10 \times (x + 8) \\ or, 9 x + 100 = 10 x + 80 \\ or, x = 100 - 80 \\ or, x = 20 \\ New average = (x + 8) \\ = 28 runs \end{aligned}

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