Aptitude Hack#54(18-4-19)

Question:
 Amit 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 

Answer:  C) 28

Explanation:
Let Amit’s average be x for 9 innings. So, Amit scored 9x run in 9 innings.
In the 10th inning, he scored 100 runs then average became (x+8). And he scored (x+8)*10 runs in 10 innings.
Now,
⇒9x+100=10×(x+8)
=>9x+100=10x+80
=>x=100−80
=>x=20
=>New average=(x+8) =28runs