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DTD1 struggling to work out the answer to 190+10 (and 290+10; 390+10 etc.). How is this taught?

(18 Posts)
DoNotAnnoy Fri 05-Sep-08 20:38:38


She has some homework where she has to add 10 to each of the given numbers she can do

No probs.

But cannot get her head around

I have tried to take her back a step to do 590+10 and 390+10 - but she just can't do it.

She feels that she can't add another 10 to teh '9' in the middle.

She can do 90+10 though.

<I was planning to break it down and say
390+10 is the same as
300+90+10 therefore
300+100 therefore

I think she will deal with the units if she can deal with adding 10 to teh "middle 9".

Any tips?

AvenaLife Fri 05-Sep-08 20:42:28

get rid off the last digits then put them back at the end, 591 would be 59, add this to 1 (not 10) to make 60, then put the 1 back to make 601.

DoNotAnnoy Fri 05-Sep-08 20:49:27

Tried that briefly at the begining TBH, she was still confused (DTD2 got it like that though).

Then I wondered if I was confusing her - because 59+1 is different to 590+10; whereas 300+90+10 isn't actually different to 390+10.

She had no problems with 29+1 and 39+1 etc in her earlier years but then I guess that was initially about counting not adding.

Maybe I just need to get her counting in 10's all the way up and over and over and it will click in the same way as her original counting when she was 3/4

Hulababy Fri 05-Sep-08 20:52:29

Remind her of her number line/number sqaure work - probably used more last year.

I have done this with DD.

So we have 54 + 10

Get her to draw a number line.
Start at 54How many tens in 10? (1)
Add one BIG line on the number line
Remind her which is the tens figure in 54 (5)
Get her to add 1 more ten to 5 tens - fingers help if nec, so 5+1 is 6
Write down the 6, then add the unit figure after it = 64

This works with other addition to too:

54 + 14

Get her to draw a number line.
Start at 54
How many tens in 14? = 1
Add one BIG line on the number line
Remind her which is the tens figure in 54 (5)
Get her to add 1 more ten to 5 tens - fingers help if nec, so 5+1 is 6
Write down the 6, then add the unit figure after it = 64 = write this number above the BIG line she drew o number line

Now look at the units - how many? (4)
Add 4 little lines to number line, after the big one
No count on from 64 (last number written on number line) until all little units counted = 68

Sounds a bit long winded written down, but DD picked this up within a couple of goes last week.

AvenaLife Fri 05-Sep-08 20:54:03

Which way do they teach it at school? If you are trying to show her one way of doing this and they are showing her another then this will confuse her. Maybe you should ask them how they do it. smile

It's OK for her to have problems understanding the homework, this just means that they need to go over it with her in class so that she gets it. Does this make sense? smile

DoNotAnnoy Fri 05-Sep-08 20:59:52

She can do all that easily Hulababy. The only time she can't do it is when she is adding to 90something. She can't work out how to add 10 to the 90.

She can do it with a raw 90, but not when it is


Avena I guess I am asking how they do teach it at school these days.

I think I will get her counting in 10's as there is absolutely no harm in this. At the end of the weekend I will get her to have another look at the homework and see if she can make it click after lots of chanting.

If anyne knows how it is taught though I would be useful to know.

Hulababy Fri 05-Sep-08 21:03:05

90 + 11

9 tens and 1 ten = 10
Write down 10 on the number line
How many units in 11?
Add the 1 to end of the 10 = 101

90 + 23

9 tens and 2 tens = 11
Write down 11 on the number line
How many units in 23?
Add the 3 to the end of 11 = 113

Hulababy Fri 05-Sep-08 21:03:37

Sorry, misread youy OP

kennythekangaroo Fri 05-Sep-08 21:08:02

Try counting in tens from e.g. 452. It is tricky crossing a hundred.

A big numberline marked in tens is a good idea.

Or show her some similar patterns with smaller more familiar numbers eg 91+10 then 191+10

At this stage of the year they are checking mental ability and will move on to splitting up numbers soon.

robinpud Fri 05-Sep-08 21:09:23

This is the first unit of the new maths framework- gosh her teacher is quick off the mark! homework an all. I shall be teaching this next week .
1. She needs to understand what each digit in 590 represents.
ie 5-means 5 lots of 100
9- 9x10
0- no units/ones.

We will be doing it with bundles of straws in 10s initially, so that they can see that adding the 10 to 590 makes the 90 into a hundred and so it becomes 600.

Get her to partition the numbers and then add on the 10 initially so she can see what is happening to each digit.
ie 590
500+90+0 so 90+10= 100 +500 = 600.

hope that helps.. have had a little glass of wine..!

DoNotAnnoy Fri 05-Sep-08 21:27:31

TY robinPud.

That was the way that I was originally going to do it.

She can partician her numbers up to 1000. She did this in Yr2. She was adding 10's in Yr2 too, but just not crossing 100. This has just got her stumped. Once she gets it she will never look back, and never have to think about it again.

She can add 10 to any number between 1 and 189 (and 200-289 etc) She just can't add 10 to 190.

She has been at school a couple of weeks already BTW robinpud, so not as quick off the mark as it sounds. DTD2 is in the other class though and she is not doing it yet (or at least not for homework)

Hulababy Fri 05-Sep-08 21:30:58

DD's school use uniblocks to do this - withh blocks to represent units, tens and hundreds.

DoNotAnnoy Sat 06-Sep-08 12:37:42

Many thanks for this.

It has now clicked and is asking me to "test" her with every x9x combo under the sun.

We started counting in 10's and realised she just didn't know where to go after 190. Once that clicked she could do all of the 190, 290, 390....but still struggled when there were units present. So we partitioned and after working through a few examples that way she can now answer them all at the click of a finger.

Once again , many thanks.

popsycal Sat 06-Sep-08 12:39:24

what robinoud said
also let me find you a link

popsycal Sat 06-Sep-08 12:40:10

excellent page to show parents how maths is done nowadays

popsycal Sat 06-Sep-08 12:41:18

this is the best bit - print it off to refer to

popsycal Sat 06-Sep-08 12:42:22

this is what I was looking foor - better still

DoNotAnnoy Sat 06-Sep-08 12:48:57

TY Popsy...i am in Leics so we usually get a hard copy of those sheets at the first parents evening.

We just havn't got them yet.

Problem has been solved now though TY.

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