Shakib's bowling average is 12.4 runs per wicket takes 5 wickets for 26 runs and thereby decreases his average by 0.4. The number of wickets taken by him till the last match was -

Question: Shakib's bowling average is 12.4 runs per wicket takes 5 wickets for 26 runs and thereby decreases his average by 0.4. The number of wickets taken by him till the last match was -

Solution:
Let, Shakib take x wickets before the last match.

Total run = 12.4x + 26
New average = (12.4x + 26)/(x + 5)

ATQ,
(12.4x + 26)/(x + 5) = 12.4 - 0.4
⇒ (12.4x + 26) = 12(x + 5)
⇒ 12.4x - 12x = 60 - 26
⇒ 0.4x = 34
⇒ x = 34/0.4
∴ x = 85

The number of wickets taken by him till the last match was = 85 wickets