Comments make this little blogger very happy.
Response to one: Sarah-Marie's Klein Bottle is here. She even has a klein bottle as a hat, and a photo of someone wearing it. Neat!
To sum up from my last post: what we were ultimately dealing with was a remainder. You don't have to break out in hives to deal with having last heard (or read) that word in the third grade. Just divide, say, 13 by 4 to find 3.25. Now, find that 3 * 4 = 12, so 13 = (3 * 4) + 1. Your remainder is 1. If you were increasing (or decreasing) by 4 stitches across 13, you would add or subtract stitches every 3 stitches and have on "extra" stitch to deal with however your heart desires. Numbers can be bigger or smaller, but they can all be tackled in this general way:
x = original number of stitches
y = number of stitches that need to be increased or decreased
r = remainder = "extra" stitches that need to be dealt with
x / y = either whole number or number in the form of a.bbbb. There could be many b's or not.
No b's? That means you have a whole number. On your way. Your math work is done. Simply increase or decrease every a number of stitches. Remember that, if you are decreasing, you will have to take into account the fact that the decreases use some of the a stitches. For example, if you need to decrease by 4 over 12 stitches, your a = 3. You will actually work 1 stitch then ssk or k2t four times, rather than work 3 and then k2t, because both a ssk and a k2t require two stitches to be worked.
If fraction, use x - (y * a) = r to find remainder.