The Law of Averages
You can calculate your bowling average as soon as you've finished bowling two games. Simply add up your scores to get a total sum. Divide that sum by the number of games you've bowled. For example, if you've bowled three games with a score of 140, 150 and 160, then you'd come to a total sum of 450. Divide that by three games played and you average 150. Your average will vary wildly in the beginning with few games bowled, but will become more consistent as you bowl more.