Sorry, this seems like a ridiculous way to do subtraction (particularly for that problem which is trivially easy). And I can’t imagine how I’d do it in my head. Borrowing seems a lot easier to me.
7 thoughts on “The New Math”
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Sorry, this seems like a ridiculous way to do subtraction (particularly for that problem which is trivially easy). And I can’t imagine how I’d do it in my head. Borrowing seems a lot easier to me.
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Something analogous to his explanation (not that format, which I never learned) is much like how I do mental math.
(4.70 out of 20? Add .30 to get to 5, then add that to the 15 that you trivially get to 20, for 15.30.
This is NOT procedurally analogous to on-paper traditional subtraction, but it’s much closer to the thing described there.)
Those yutes will make great programmers… for someone else to hire.
/* calculate d = a – b */
/* like we were taught in school */
sum = 0
do
c = random(b) ‘pick a random number from 0 to b
sum = sum + c
if (sum < b) then
a = a – c
else
/* the sum is too big! Mr. Honeycut never covered that! */
extra = sum – b
a = a + extra /* I think this might work */
sum = sum – extra /* or maybe not */
loop while sum b /* which is forever if the random generator is being a meany */
return some
/* Bob, why can’t I just use d = a – b? */
George… what did you do, copy and paste that from the source code for the obamacare website? 😛
As the article states, this is how I used to make change all the time when I worked in shoe stores and Radio Shacks. And I could do it rapidly – so rapidly that often the customer would become suspicious that I had somehow short changed them. Even today I can do it very fast.
BUT, the advantage to making change this way is that I didn’t have to remember anything because I put the coins in my hand as I worked up from the price to the money given. Well ok I had to remember that last total I made. Pretty trivial.
I think it would be much harder if I had to remember all the bits of change needed as I went along and *then* took them out of the cash drawer.
Any time I worked in retail, and had a register that told me the change for a transaction, I would pull the bills and coins from highest-to-lowest, but then would still count it back coins first, then lowest-to-highest bills (“Your total was $3.22. And 78 makes 4, 5, 10, aaand 20.”)
If one works a register long enough, you learn the coin counts for just about any change amount, including the “holy grail” of 41 cents.
When making change at a fundraising stand or other stand-alone cash-box kiosk, making change by counting up from the total is MUCH easier, for sure.
Since the old way of learning math never got us anywhere (besides the Moon), I can well understand why we really need elite educated (in the old method of learning math ironically enough) people to find a more complicated way to do such a trivially easy thing. I suspect that in a few years this revolutionary math will put the US far ahead of other nations in the area of math skills. I feel sorry for our foreign competitors, as they do not have the advantage of such advanced mathematical teaching techniques.
My memory isn’t good enough to borrow. I’m not that visual. I always forget what the new amount after I borrowed is, I forget what the ones digit was by the time I get to the hundreds, whatever. I was never taught this, but this is the only way I can do mental arithmetic.