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Easy way to remember the subtraction and addition

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surendranathisaac 19 September 2013 07:18
Posts6
Joined15/08/10

Easy way to remember the subtraction and addition, Subtraction of 9=10-1; adding one to the unit place of the numbers  

 

18-9= 18-10+1=8+1=9

17-9=17-10+1=7+1=8

16-9=16-10+1=6+1=7

15-9= 15-10+1=5+1=6

14-9= 14-10+1=4+1=5

13-9= 13-10+1=3+1=4

12-9= 12-10+1=2+1=3

11-9= 11-10+1=1+1=2

 

Subtraction of 8=10-2; adding two to the unit place of the numbers

17-8= 17-10+2=7+2=9

16-8= 16-10+2=6+2=8

15-8= 15-10+2=5+2=7

14-8= 14-10+2=4+2=6

13-8= 13-10+2=3+2=5

 12-8= 12-10+2=2+2=4

11-8= 11-10+2=1+2=3

 

Subtraction of 7=10-3; adding three to the unit place of the numbers

16-7= 16-10+3=6+3=9

15-7=15-10+3=5+3=8

14-7= 14-10+3=4+3=7

13-7= 13-10+3=3+3=6

12-7= 12-10+3=2+3=5

11-7= 11-10+3=1+3=4

 

Subtraction of 6=10-4; adding four to the unit place numbers

15-6= 15-10+4=5+4=9

14-6= 14-10+4=4+4=8

13-6= 13-10+4=3+4=7

12-6= 12-10+4=2+4=6

11-6= 11-10+4=1+4=5

 

Subtraction of 5 =unit place numbers+5

14-5= 4+5=9

13-5= 3+5=8

12-5= 2+5=7

11-5= 1+5=6

 

Subtraction of 4

4=1+3; 2+2     subtract the difference of the unit place numbers from 10

13-4= 10-1=9

12-4=10-2=8

11-4=10-3=7

Subtraction of 3

3=1+2  subtract the difference of the unit place numbers fr0m 10

12-3= 10-1= 9

11- 3= 10-2=8

 

                                                                                                      

ADDITION

Adding 9 to the numbers

9=10-1; subtract one from the numbers+10

9+9=10+ (9-1) =18

8+9=10+ (8-1) =17

7+9=10+ (7-1) =16

6+9=10+ (6-1) =15

5+9=10+(5-1)=14

4+9=10+(4-1)=13

3+9=10+(3-1)=12

2+9=10+(2-1)=11

Adding 8 to the numbers

8=10-2;subtract two from the numbers+10

8+8=10+(8-2)=16

7+8=10+(7-2)=15

6+8=10+(6-2)=14

5+8=10+(5-2)=13

4+8=10+(4-2)=12

3+8=10+(3-2)=11

Adding 7 to the numbers

7=10-3; subtract 3 from the numbers+10

7+7=10+(7-3)=14

6+7=10+(6-3)=13

5+7=10+(5-3)=12

4+7=10+(4-3)=11

Adding 6 to the numbers

6=2+4;1+5 ;make 10 and add the remaining number

6+6=(6+4)+2=12

5+6=(5+5)+1=11

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starstories 12 August 2014 06:58
Posts1
Joined29/07/14

hi, this is great post, for parents to maintain our chil's perfectly with mathametics techinics.

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JLPearson 14 August 2014 10:02
Posts38
Joined21/05/13

There is clearly a pattern here that could be helpful, but the emphasis is on the manipulation of numbers and symbols with little to support developing any understanding. I suspect that if a child could follow what is going on here then it wouldn't be needed anyway. The key is to see the patterns.

Does replacing one step, such as add 7, with two steps (add 10 then subtract 3), really make calculation easier? Using a model to represent the numbers would be a better approach. Perhaps a bead string or a number line, or even the current trend, a bar model.

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Christina99 03 December 2015 10:36 - Last edited by ncetm_administrator on 18 January 2018 13:09
Posts1
Joined03/12/15

The content of this post has been removed, as it doesn't comply with our terms of use.

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helenjw 03 December 2015 11:34
Posts54
Joined15/05/08

I have to agree with JL Pearson. Better still to look at the patterns when arranging a staircase of Cuisenaire rods or Numicon pairs.

 

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Name withheld 19 September 2017 08:29
This post has been reviewed during our moderation process and blocked because it breaches our terms and conditions
  

Name withheld 04 October 2017 11:56
This post has been reviewed during our moderation process and blocked because it breaches our terms and conditions
  

Name withheld 12 January 2018 09:34
This post has been reviewed during our moderation process and blocked because it breaches our terms and conditions
  

helenjw 17 January 2018 22:36
Posts54
Joined15/05/08

What is going on with this thread, please, NCETM?

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helenjw 18 January 2018 13:00 - Last edited by ncetm_administrator on 18 January 2018 15:25
Posts54
Joined15/05/08

 

Thank you for your email ncetm administrator - but it is a 'do not reply' address and yet you ask me to reply and explain! ! This was my email: 

I have had a number of alerts from this thread and when I open them & the messages on the thread reads: "This post has been reviewed during our moderation process and blocked because it breaches our terms and conditions” maybe the thread needs to be shut down? Or can I mute this?
 
 
 
Helen Williams

 

 

 

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