Page 4 | To ask if you do long multiplication/division regularly?

BoyTree · 2020-12-10T15:34:32+00:00

Please settle a debate for me! Older son is doing long multiplication and it came up that it would have been more important to know the formal 'method' to complete the sum by hand/brain when calculators weren't so ubiquitous. He asked who would still be doing it by hand now and I was stumped! I can't think of anyone who would routinely do long multiplication using the column method as part of their job, but felt sure I was probably overlooking some vital role. Does anyone here use it or know of a job where this skill would be vital?

PickAChew · 10/12/2020 23:36

Not on paper but I'm fairly good at chunking up or down in my head and if my head says no, my phone can do it.

chomalungma · 10/12/2020 23:37

@FangsForTheMemory

I do long division occasionally. If it’s one or two sums, I can do it quicker on paper than on my phone.

Something like 2145 / 19?

Long division is strange as you still have to do division (or multiplication) to get the final answer.

chomalungma · 10/12/2020 23:38

If you know your math facts it's not that difficult to do it, so why bother with the calculator

78365 / 37

What maths facts help with that calculation?

Brighterthansunflowers · 10/12/2020 23:54

Never! I wouldn’t even know how to anymore without googling tbh. I enjoyed and was good at maths when I was at school, but haven’t done it for 20 years.

What i find is useful is being able to guesstimate calculations. If I know roughly what it should be, I can spot if I’ve done the calculation wrong or put a decimal point in the wrong place.

ChestnutStuffing · 11/12/2020 00:17

@chomalungma

If you know your math facts it's not that difficult to do it, so why bother with the calculator

78365 / 37

What maths facts help with that calculation?

I don't understand the question, how would you even attempt to do that by long division without knowing math facts? Counting on your fingers? Diagrams?

FangsForTheMemory · 11/12/2020 05:14

Chomalungma is just picking examples of complicated long division to prolong a tedious argument. The long division I have to do is never that complicated. It’s usually connected with changing recipes or similar.

Saracen · 11/12/2020 05:23

I do it maybe 4x a week, not for work. Usually it is because I CBA to go get a gadget to do it for me though. I don't think it would be an issue for me if I didn't know how. If I needed to do it regularly, I would carry a phone about with me which had a calculator function.

A skill which I do think is essential is the ability to estimate, so that when using a calculator you know whether you are doing the correct calculation or have pressed the buttons properly.

imamearcat · 11/12/2020 05:47

I've got a maths degree with quite a mathsy job and I never do long multiplication or devision.

ClarenceBoddicker · 11/12/2020 06:04

Think some including me are getting mixed up with the usefulness of long division and usefulness of understanding mathematics. Will trust the maths teacher on the former but find the just use a calculator on your mobile phone comments depressing like it’s pointless to understand basic arithmetic

BarbaraofSeville · 11/12/2020 06:09

Not division but I often write calculations out by hand as it can help with the thought process and/or 'show my working' to supervisors or clients but I do have a technical job.

I agree with the poster who said you need to understand the fundamentals in order to know when you've arrived at a stupid answer. Too many people plug the numbers into their phone calculator and take the result as gospel and don't notice if there's a mistake.

Incidentally, I'm also having to refresh DP on trigonometry (SOH CAH TOA and all that) as he needs it as part of what would appear to be a totally unrelated practical field.

Prior to this, he was certainly of the 'why are we learning this when I'll never need it in real life' opinion.

listsandbudgets · 11/12/2020 06:43

DP does quite a bit of trading on the stock markets and does that sort of thing in hos head - he needs to be quick as opportunity can come and go.at speed.

I dint do it very often but I think being able to use column method helps people understand how it works and apply to other areas of.maths and science. Just using a calculator provides no understanding really

chomalungma · 11/12/2020 07:53

@FangsForTheMemory

Chomalungma is just picking examples of complicated long division to prolong a tedious argument. The long division I have to do is never that complicated. It’s usually connected with changing recipes or similar.

That's not long division - that's usually short division.

What do people think long division is?

The long division that means you have to work out 'how many 37s go into 294' as part of it has maths facts that really are using division as part of long division.

chomalungma · 11/12/2020 07:57

@ClarenceBoddicker

Think some including me are getting mixed up with the usefulness of long division and usefulness of understanding mathematics. Will trust the maths teacher on the former but find the just use a calculator on your mobile phone comments depressing like it’s pointless to understand basic arithmetic

I totally agree with understanding basic arithmetic and with also being able to use maths facts to see if your answer is correct.

Going back to my complex long division question :

78365 / 37 is about 80,000 / 40 - so an answer of around 2000 is what you are looking for.

(The actual answer is 2117.973)

chomalungma · 11/12/2020 08:01

I don't understand the question, how would you even attempt to do that by long division without knowing math facts? Counting on your fingers? Diagrams

When you start to do that complex division question, you have to either use 37 x tables maths facts, 37s table division facts or repeated addition of 37 to work out a division question which involves 37.

Not the kind of maths facts people have that their fingers. Maths skills (including division) are needed so you can do a more complex division.

steppemum · 11/12/2020 08:06

yes i use it.

usually itdoesn't occur to me to get out my phone.
So, eg when buying paint/fabric etc I will quickly double check if that pot will be enough.

Long division less so. If I do it is usually approximate, so I only do the first bit!

But I teach 11+ students, so my skills ar every fresh and practiced. If I hadn't done it for a while maybe I would reach for the calculator.

steppemum · 11/12/2020 08:12

@chomalungma

I don't understand the question, how would you even attempt to do that by long division without knowing math facts? Counting on your fingers? Diagrams

When you start to do that complex division question, you have to either use 37 x tables maths facts, 37s table division facts or repeated addition of 37 to work out a division question which involves 37.

Not the kind of maths facts people have that their fingers. Maths skills (including division) are needed so you can do a more complex division.

hmm, well yes but no!

So I looked at your example, and in my head I could quickly see that the first 2 numbers would be 21.
That is simply because - how many 37 in 78? 37+37 =74.
which leave 4 over, so then how many 37 in 43
That isn't really needing to know my 37 times table, it is simple addition and subtratcion.

It is highly unlikely that I would do it in my head/on paper if I needed to know the actual answer, but if I was working out - will this be enough/too much for something then that is all I need to know.

chomalungma · 11/12/2020 08:14

That isn't really needing to know my 37 times table, it is simple addition and subtratcion

Ok

1326 / 17

A relatively low number and a number less than 20

StCharlotte · 11/12/2020 08:22

Not regularly in this job but have used it more in other jobs. Secretarial. Oh and I used algebra daily in one legal role and was very grateful for it.

I can remember my (much older) BIL teaching me long division before I learnt it at school. School was very impressed I picked it up so quickly!

I actually really like arithmetic.

chomalungma · 11/12/2020 08:23

And if you think it's simple addition and subtraction......

70044 / 78

With an explanation of how you worked out each step

Please

BogRollBOGOF · 11/12/2020 08:27

Long division has never computed in my head. I didn't pick it up in y6 maths. I confessed in y10, several of my friends also confessed to struggling and our teacher sat down to explain. DH has also had a go.

I did get the hang of long multiplication in end. The stage of shifting Ts & Hs along in place value evaded me for a while.

I'd spot if a calculation was way off and could handle rounding off to how many 40s in 300 rather than 37s in 294. That's manipulating number facts rather than truely dividing.

Numbers wriggle in my head and I need a piece of paper to put them doen in one spot.

steppemum · 11/12/2020 08:29

@chomalungma

That isn't really needing to know my 37 times table, it is simple addition and subtratcion

Ok

1326 / 17

A relatively low number and a number less than 20

well, same applies doesn't it?

If I was standing in a shop and trying to work something out, I would.
In this case I'd probably go from 15x table which is something most of us know without realising they do. (15, 30, 45, 60 is a number pattern most of us know)
so 15 x 8=120, plus 16 (to allow for the difference between 15 and 17) Oh thats too big, it must be one less
so 17 x 7, so first number is 7,

So anwer is between 70 and 80.

For most things that you do apporximately, that would be enough, probably wouldn't bother to do more, if I needed to I would need to jot it down on paper.
But if you know how to do it, it isn't hard.

You seem determined to prove that people can't and won't.
But for many of us, we are telling you, we can and do!

Livpool · 11/12/2020 08:31

No and wouldn't know how to do it!

Maths was never my strong point

EsmeShelby · 11/12/2020 08:32

I do when I am sense checking a formula on a spread sheet.

steppemum · 11/12/2020 08:34

@chomalungma

And if you think it's simple addition and subtraction......

70044 / 78

With an explanation of how you worked out each step

Please

I'd need a bit a of paper for that one. But this time it is simple multiplication 78 x 9? or maybe x 8? would be my first try, and that I can do in my head. Most children aged 8 can do 78 x 9 without trouble (on paper obviously) It really is not rocket science.

ArosAdraDrosDolig · 11/12/2020 08:37

Not one single time have I needed to do long division or multiplication. Including for gcse maths.

I don’t use maths in everyday life. I really don’t. Perhaps if I had gone into a different career i might.