# Mumsnet Talk

## In not being able to do my 10 year olds math homework!

(147 Posts)
Livesforbedtime Wed 05-Mar-14 18:51:11

I don't understand this.. She has to work out 23 x 22..

Now I'm not the sharpest pencil in the box, but I have a degree and a responsible job... So WHY when I worked it out as:

20 x 20 = 400
2 x 3 = 6

But it's not is it? It's 506.. But I don't understand why

My poor 10 year old DD is bewildered.. And I cannot understand why I'm wrong yet I know I am!

I suspect it have a mind block... Yes that's it.. I'm not truly stupid ok I might be..

It doesn't make sense!

RedPencils Wed 05-Mar-14 21:12:18

DS1 left me behind in Year 4. He is frighteningly good at mental arithmetic and times tables. I'm shocking!
I've been known to sneak a look on the calculator on my phone, under the guise of checking a text message to check the answers.

Livesforbedtime Wed 05-Mar-14 21:14:19

Red.. That's how I knew it wasn't 406

DimeBar Wed 05-Mar-14 21:31:24

I fucking hate the grid method.

I work with 16+ students doing GCSE, they're aiming for a C grade.

Give them a calculation such as 3.75 x 2.35, they get the grid correct, then give up because the numbers are too big/many to add, or they transpose the numbers incorrectly when transferring from the grid to put into columns, getting the sum wrong.

Show your kids the column method, it's so much easier in the long run.

I often wonder how scientists/mathematicians will cope in the future when half a page is taken up with one small calculation.

And breathe

Impatientismymiddlename Wed 05-Mar-14 21:35:19

Bloody chunking and gridding methods confuse us oldies who only learned the bus stop method.
I could work that out using any of the methods but my husband would struggle with anything except the bus stop method.

TheGreatHunt Wed 05-Mar-14 21:39:19

Scientist will use a calculator.

anothernumberone Wed 05-Mar-14 21:53:42

Holy crap that grid thing is complicated. I am all for exploring ways of making maths easier for students, I teach maths physics so I spend my days doing it but man that seems difficult. Do children really find it easier?

Logg1e Wed 05-Mar-14 21:56:01

The grid method is simply a precursor to the long multiplication algorithm.

BigPawsBrown Wed 05-Mar-14 21:57:43

I do not understand a word of this thread.

Wed 05-Mar-14 21:58:47

Why would anyone do 3.75 x 2.75 in a grid method?

It's enough to know it's about 4 x 3 or 3 x 2 3/4

The grid method is easy if you understand numbers and what you are trying to achieve

When was the last time you did long multiplication?

e.g. 52 x 31

Well - you've got 30 lots of 52 and 1 lot of 52

It's like long multiplication but laid out differently.

30 lots of 52 is 30 lots of 50 and 30 lots of 1

anothernumberone Wed 05-Mar-14 21:59:37

Logg ie not here in Ireland it is not taught here or at least dd didn't do it, thank god.

Wed 05-Mar-14 21:59:48

Chunking - it's what many people do when they do estimating division in their head.

Wed 05-Mar-14 22:02:45

Do people who like the long multiplication actually understand how it works?

It's the grid method - but in a different format but exactly the same principles.

22 x 31

22
x31
....
22 (1 x22)
660 (30 x 22)
....
682

Chunking

682 / 22

30 x 22 = 660 (leaves 22)
1 x 22 = 22 (leaves 0)

And that's chunking.

Wed 05-Mar-14 22:07:29

And doing 3.75 X 2.75 by long / short muliplication.

Would people really do that? In the real world where maths is used daily?

anothernumberone Wed 05-Mar-14 22:08:01

Interesting Kim I have never taught if that thankfully I get to use a calculator so I haven't had to think about it for a while. That though is far less complicated than adding a variety of different combinations of the chunks though.

Wed 05-Mar-14 22:12:17

It's just working up or down in multiples of 10 until you get near the answer.

You need to know your times tables though.

I really think it's important children can understand why a method works - in any way possible rather than being told a method like the bus stop method. They might get the right answer but do they have a sense that it's right.

I love diagrams, pictures anything to get the children to understand a problem.

Except DS insisited on drawing a Kg mass out when he had to work out what 1 1/2 kg of sweets cost. He then draw 1/2 kg weight next to it.

DrCoconut Wed 05-Mar-14 22:18:48

I'm always amazed at how many people don't know the basics. I taught a maths session for adults once and some of them couldn't work out a simple percentage, or change from a fiver without a calculator. The same people have learned to read OK. Being basically numerate is as important is literate. Britain (in general) takes a perverse pride in poor maths skills and I can't understand it. Not blaming anyone here, we have a long term national issue with this and it will not be rectified overnight. The constant changing of methods may or may not help. It can be a good thing if a previous method was not working, or cause confusion.

Wed 05-Mar-14 22:19:07

I learned in Ireland in the 1980s and this is how we did it:

23
X
22
---
46 (2x3 = 6; 2x2 =4)
+460 (put a zero on the end then 2x3; 2x2)
--
506

What's that method called?

Wed 05-Mar-14 22:22:20

Well, I saw it was times 22. Cant do that, but I can do by times 11. So 23 times 11 is 253.

Do it again, add together 506.

Wed 05-Mar-14 22:25:37

It's the grid method principle.

You put a zero at the end because the 20 in 22 is worth 20.

So it's 20 x 23
2 x 23

Clake66 Wed 05-Mar-14 22:37:36

Lost the plot with my daughters maths student teacher or student maths teacher who set homework. Using an example with a wrong answer, so for me trying to get the homework done was impossible. I asked my A level maths husband to sort it out, who after a quick glance rather than showing her how to do it, told me to write a note to the student teacher in my daughters homework book in red "to please see me after school!" Even though she was wrong, she would not admit it! He sat and helped the next evening showing how the calculations were done in an easier way with working out shown and a further note to the head of maths to be handed in at reception.
Really annoys me that it seems only one way is allowed to get children to understand calculations they may never use again. Or have attitudes like my maths teacher that those less able won't need Pythagoras, or need to know how to calculate the area of a circle anyway....while his brother the science teacher saw everyone with the potential of the next Einstein.
Please do not get me onto teachers who cannot spell!

Wed 05-Mar-14 22:41:05

"Really annoys me that it seems only one way is allowed to get children to understand calculations they may never use again"

I agree - children need to understand a problem and think about the maths needed to solve it. Then they need a method - whatever works for them - to solve it.

But it's understanding the problem that's key. Even A grade students get flummoxed if given a problem but no obvious clue to the actual maths to do it.

Nocomet Wed 05-Mar-14 22:45:49

DD2 obtained permission only to use the grid method for the first couple of questions in any multiplication HW.

DH taught her the normal column method back in Y3/4.

The grid method reduces her to a gibbering wreck. (She's dyslexic and all the neat drafting of a grid to help doesnt turn out neat and it doesn't help, it just makes steam come out her ears).

BigRedBall Wed 05-Mar-14 22:47:30

23 x
22

46
460 +
_
506
_
1 (carried over from 4+6 and added to the 4)

littledrummergirl Wed 05-Mar-14 22:52:44

Ds2 yr 7 asked for extra support with his maths. I bought a year 7 coursebook which has a paragraph of multiplication. 5 days ago I printed some 2figure questions of the kind above, showed him the method and sent him off to do some.

He got them all wrong!

I found the grid method today and showed him that and he told me he knows how to do it. Got the first 3 right.
I explained the proper method again writing H T U above the columns and he got them all right

Ds1 yr 9 at a grammar then told me he had never
seen the proper method!

anothernumberone Wed 05-Mar-14 22:53:35

Taking chances dd learned the same way this year things have not changed much.

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