I like to do long division without multiplying cumbersome numbers, if the problem permits it. In baseball statistics, that is often the case.
The Cardinals, we will suppose, will win against the Cubs this afternoon, and improve their record to 71-51. Now, I know immediately that that is just a tick under .583, because that's what 70-50 is. But suppose I really want to do the division, but I don't feel like multiplying by 122. Here's what I do to find remainders:
First, I notice that the initial digit is going to be 5. That's because I know that 72-48 = .600, and 71-51 isn't as good as that.
Second, I multiply the DIFFERENCE between 71 and 51, by 5. That gives me 100, and a new ratio: 100-22. See, the one number goes up by 29 and the other goes down by 29, or I just think, well, 122-100 = 22.
Third, I look at 100-22 and I say, the next digit is going to be 8. That's because 80-20 = .800. Now then, every win PAST 80 is worth 2 points to the good, and every loss PAST 20 is worth 8 points to the bad. That gives me 24 points, so my next ratio is 24-98.
I look at 24-98, and I notice that it is almost exactly 1-4, which is .200, so I stop here and say that the winning percentage is .582.
If I wanted to continue it, though, I would say that the next digit has to be 1, and I'd notice what was SHY of 1-4 or .200. Namely, there are two losses too many. Each of those losses is worth 8 points. So I now have the ratio 106-16, and I just keep on going from there.
I never multiply anything by 122. I never subtract any three digit number from another three digit number. I have a slew of tricks like this, all because of baseball....