A cricketer has a certain average runs for 10 innings. In the 11th inning, he scores 100 runs, now his average is increased by 9 runs. Then average of 11 innings is:

10 runs

Let the old average of the cricketer be x.

According to the question:

\(\frac{\text{10x + 100} }{11 }\) = x + 9

10x + 100 = 11x + 99

x = 1

The old average of the cricketer comes out to be 1. Thus, the new average = x + 9 = 1 + 9 = 10 runs.