Support NeoGAF

[Desperado]

I thought long division is dealing with polynomials not numbers and division is with just numbers.

Polynomial division briefly appears in upper level Abstract Algebra but I haven't seen this technique used anywhere else since middle school math class. Division, on the other hand, seems to be more useful and used more often.

You're thinking of synthetic division.

I've got problems when I'm dividing by something with 2 numbers. That's probably because the brilliant way we learned that in 4th grade was my teacher would show 3 classmates, and they would show everyone else.

eh? explain what you mean by "something with 2 numbers."

 

[Loki]

Wait, so you guys don't/can't do division in your head? Because I can (and I assumed most others could also, at least for smaller #'s), and when I analyze it, the technique I use is long division. For instance, if I want to divide 668 by 7, I do:

7 into 66 = 9 rem. 3
7 into 38 = 5 rem. 3
7 into 3.0 = ~.43

So you get 95.43 as an answer. That's basically a long division process without writing everything down.


So isn't this how you guys do division in your head also, or do you use some other method? I remember learning synthetic division (which a previous poster mentioned) many years ago and thinking, "oh, this is pretty cool," but I can't remember the exact technique. Also, wasn't synthetic division used for dividing polynomials by either binomials or other polynomials (rather than numbers), or am I entirely off base? We're talking at least 9 years ago here, so cut me some slack.

 

[Memles]

I use long division to average out test scores all the time and figure out how many points I lost on the term and fun stuff like that...I sometimes even choose it over a calculator, to be honest with you. More fun that way. It's really not that difficult, only incompotent teachers could make it that way.

 

[human5892]

So isn't this how you guys do division in your head also, or do you use some other method?

I sort of do it like that...it's more of a reverse engineering process for me, though. Using your example of 668 divided by 7:

- 9*7=63, so the first number is 9
- 3 leftover, so
- 5*7=35, so the next number is 5
- 3 leftover, so
- 4*7=28, so the next number is .4

(continued indefinitely until I have a precise enough figure)

I also visualize the numbers as they would appear on paper in an actual division problem.

 

[Desperado]

anyone else do it that way?

 

[Loki]

I've seen it done that way before, Desperado-- I think one of my friends does it that way.

 

[CrystalGemini]

Not the stuff about cursive though. Who needs cursive?

I use cursive. As my primary "style" of writing. I find it's more efficient seeing as almost every letter flows into the next. And it looks nicer. Although I do use print when I have to write certain documents to dumb people (ie. gov. agencies, post office...etc.)

 

[CrystalGemini]

anyone else do it that way?

Wow. I've never seen it done that way. O_O I use the method on the left. Where did you learn that?

 

[Deleted member 1235]

anyone else do it that way?

oh, I thought that stuff on the right was standard division... I guess I do know. I don't know what the hell is going on in the left anymore tbh

 

[Gorgie]

They really should ban calculator use in math for all stages of schooling, especially high school. Someone in Grade 11 asked me at work what 6 x 4 is while doing inventory. Sad, but true.

 

[akascream]

Lol, I love the ad at the bottom of the page while reading this thread.

:lol

 

[TheOMan]

Hmm, I'm not really sure how one forgets how to do long division. I'm thinking that those of you that think you forgot could probably do it with a quick refresher. I do it in my head every day, it's pretty much necessary. I can't believe how early calculators are allowed to be used in MATH classes now. :/

 

[Desperado]

Wow. I've never seen it done that way. O_O I use the method on the left. Where did you learn that?

either from a teacher or I taught myself to do it...can't remember.

It's basically the same thing except when you multiply the divisor [left number] times the digit in the quotient [top number], you have to subtract from the digit in the dividend in your head..

 

[Wendo]

anyone else do it that way?

OH MY GOD.

Where were you twelve years ago? Jesus, that would have made a HUGE difference for me when learning division.

 

[Cubsfan23]

Wait, so you guys don't/can't do division in your head? Because I can (and I assumed most others could also, at least for smaller #'s), and when I analyze it, the technique I use is long division. For instance, if I want to divide 668 by 7, I do:

7 into 66 = 9 rem. 3
7 into 38 = 5 rem. 3
7 into 3.0 = ~.43

So you get 95.43 as an answer. That's basically a long division process without writing everything down.


So isn't this how you guys do division in your head also, or do you use some other method? I remember learning synthetic division (which a previous poster mentioned) many years ago and thinking, "oh, this is pretty cool," but I can't remember the exact technique. Also, wasn't synthetic division used for dividing polynomials by either binomials or other polynomials (rather than numbers), or am I entirely off base? We're talking at least 9 years ago here, so cut me some slack.

Let's see for that equation, I would do 7 x 90 =630

668-630= 38

7 goes into 38 5.43 times

so 90 + 5.43= 95.43

I guess it helps if you know how to do percentages in your head too

 

[Wraith]

For 668/7 I would say:

7 into 700 100 times. 32 left over ~ 4 times, with half of one left. Subtract that from 100, so I'd come up with 95.5. I'd then arbitrarily downgrade that(since it's a little over a half left over) by a little bit and probably come up around 95.4. That final decimal place can blow me.

 

[Seth C]

Cursive really is useless. It may be faster for some, but only slightly. The time spent learning it in elementary school could be put to better use. I stopped using it for anything but my signature in 6th grade. By sophomore year in highschool I stopped using it entirely.