Short division

(23 Posts)
Phosphorus Fri 25-May-18 11:05:19

Help!

I am not an idiot, I get algebra, circle theorem, lots of GCSE stuff.

But how do you do 37/5 using short division!?

I keep getting 11.

I know the answer is 7r2. But..really!?

OP’s posts: |
Phosphorus Fri 25-May-18 11:06:27

Sorry, 39/5

OP’s posts: |
Phosphorus Fri 25-May-18 11:12:54

Oh God, don't worry!

I was carrying the wrong number.

9 year olds have better skills than me.

OP’s posts: |
TeenTimesTwo Fri 25-May-18 11:13:05

Bus stop?

5s into 3 won't go, carry the 3.
5s into 37 goes 7 r 2 because 5x7 = 35.

5s into 3 won't go, carry the 3
5s into 39 goes 7 r4 because 5x7=35

A better example 87 divided by 5

5s into 8 goes 1 (one time), carry the remainder 3
5s into 37 goes 7, remainder 2

Sorry, can't do fancy pictures

TeenTimesTwo Fri 25-May-18 11:13:52

user789653241 Fri 25-May-18 11:18:14

@TeenTimesTwo , I don't get the point of short division. Is there any reason they teach this method?

TeenTimesTwo Fri 25-May-18 11:23:48

If it is the 'bus stop' method I described?

I'm tempted to ask how else you would do eg 13565 divided by 5

5s into 13 goes 2 carry 3
5s into 35 goes 7, no carry
5s into 6 goes 1 carry 1
5s into 15 goes 3 no remainder

So answer is 2713. Is there another method?

TeenTimesTwo Fri 25-May-18 11:24:35

Though I agree pointless for 37 divided by 5, as that's just times tables, but you have to start somewhere.

TeenTimesTwo Fri 25-May-18 11:36:48

One thing I have found, is once some children have learned a method, they start applying it to stuff even though it is pointless.

So if the DC in question has just learned bus stop, they might start using it even for questions where it is just times tables needed (eg the 37 divided by 5 question). They don't seem to notice that their first step is entirely pointless.

sirfredfredgeorge Fri 25-May-18 11:56:32

I'm tempted to ask how else you would do eg 13565 divided by 5 grin

13565 / 10 = 1356.5
1365.5 * 2 = 2713

but perhaps the /5 is just not the best example...

user789653241 Fri 25-May-18 12:06:00

I have no clue about bus stop methods.

The reason I asked was, my ds was doing some homework while back using short division and he wasn't happy, and I asked him why he isn't using other methods. He said he had to do it that way. I don't think I never learned the myself as a child.
It just looked like incomplete long division to me.

TeenTimesTwo Fri 25-May-18 12:40:26

sirfred You are quite right. Maybe dividing by 7 would have been a better example.

Irvine it is 'incomplete long division' if you want to put it like that. You don't need the full long division because for 'short division' you should know your times tables and the carry over is only ever going to be 1 digit so easy to track.

So how else would you do e.g. 23564 divided by 6? <genuinely interested as I'm not sure I can see another good method>

TeenTimesTwo Fri 25-May-18 12:41:28
sirfredfredgeorge Fri 25-May-18 13:23:35

So how else would you do e.g. 23564 divided by 6? <genuinely interested as I'm not sure I can see another good method>

In my head, I just did this:
4000 is 24000
so (436 / 6) is made up of 420 and 16 so that's 72 and 2/3
3927 and 1/3

Which I don't think is that bus stop method, as I find the most significant digits differently?

TeenTimesTwo Fri 25-May-18 13:31:51

sir And you think that's easier?!

No, not the bus stop method. You've done a bit of chunking and some clever rounding/subtracting.

But would you really do that as your written method if you had pen and paper handy?

sirfredfredgeorge Fri 25-May-18 13:43:06

Easier for me certainly, and it's how I would've done it with paper too, but then I wouldn't've likely ever done anything with the paper other than note down the intermediate numbers. I don't have a written method for any numerical calculations I don't think. I either do things in my head which I think is based around what people call chunking around here - or I use the computer that is always in my hands...

TeenTimesTwo Fri 25-May-18 13:48:07

I don't have a written method for any numerical calculations I don't think.
That's quite impressive. I'd better not ask how you do long multiplication!

(But bus stop is still generally considered easier as a written method.)

user789653241 Fri 25-May-18 15:36:05

For me, I just use long division. It doesn't matter divisor is single or multi digit, that's how I learned.

sirfredfredgeorge Fri 25-May-18 18:26:33

I'd better not ask how you do long multiplication!

It's still just chunked up into parts, and rely on my working memory to help with the different chunks.

I'm also almost never away from a computer, and haven't been since I was little, even most of my primary school differentiation was being told to go see if I could figure out what those new BBC machines did.

TeenTimesTwo Fri 25-May-18 19:05:02

sir I think your working memory must be better than mine, which I think has gone rusty!

Irvine using long division is fine. I'm just lazy so don't want to write down numbers I don't need to!

sirfredfredgeorge Fri 25-May-18 19:14:15

sir I think your working memory must be better than mine,

The various tests I've done in some neuroscience research where I've been a guinea pig suggest it's very, very good yes.

sirfredfredgeorge Fri 25-May-18 19:16:43

Oh, and I'd also say it appears to be something that DD has inherited and she equally finds primary maths easy despite not having a huge interest in it, and no real desire to practice.

TeenTimesTwo Fri 25-May-18 19:21:41

Sadly, my DDs haven't inherited any maths genes from me.
But maybe that's not surprising since they're adopted.

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