I worked with lists of winning numbers for Pick 3 FL.

Here is example:

I take result from 4th column, one prior to the game I am trying to guess. Say, it is 327. I use 3 and 7, multiply, get 21. 

I add up to 10# , and get : 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31. I multiply them by 4, get 40 tickets, Front and Back pairs. 

Result of the game I was seeking is 412 . That means I won pair 12, $50, but spent $40. Pure profit $10.

Another example: combination in a forth column is, say, 596. I multiply 5 by 6, get 30, add 10: 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40. I flip those numbers and use them each also for Front and Back pairs, that makes for 40 tickets. When game results come in, it's 838, meaning, I won twice, pair 83, and 38, so it's $100, but I spent $40. Pure profit $60.

Yet, if I keep playing the same trend, I will end up eventually spending more than winning, even though I will profit $10 here and there and quite often, $60 here and there, yet also have loosing combinations. 

It ended up being nerve wracking trend.