How do you calculate a bowling strike rate in cricket?

A bowlers strike rate is calculated by dividing the number of balls he or she has bowled by the number of wickets taken with those balls.

For example if a bowler has bowled 2000 balls in his career and has taken 50 wickets, he has a bowling strike rate of 40.00. In other words the bowler has taken, on average, a wicket every 40 balls.