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2+2 is not 5 and Singapore


sleepymommy
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Ds7 has known his math facts for awhile now but I just want him to keep practicing because he tends to forget or get slower with them after some time.

 

I picked up the book "2+2 is not 5" from B&N today because I remember reading some good reviews of it on here. It's a pretty straightforward book with lots of math 'tricks' in it.

 

For example, for adding 9s it is called Magic 9s:

 

9+8 = 17 because 7 is one less than 8, then put a 1 in front.

 

or 9+5= 14 because 4 is one less than 5, put a 1 in front.

 

This is different from SM's 'make ten' method.

 

Another example would be "Number in the Middle":

 

6+4 = 10 because 5 is the number b/w 6 and 4 and you double it.

3+5 = 8 b/c 4 is the number b/w 3 and 5 and double it.

 

I think it's nice to have an arsenal of math tricks in you back pocket to help when you need it, but I also don't want to confuse him with too much and cause him to over think about simple addition.

 

My question is do you think it would confuse him OR conflict with the way he has learned math via Singapore method?

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I don't use Singapore, but I tried the book last year with my dd 8.5 to help her with math facts, and it did not help her at all. It became too many "tricks" to try to keep track of, and a full black and white page of math facts was just too much and would cause melt down. I like some of the tricks, personally, but it works better for me to just remind her to make 10 when adding 8 or 9, or doubles plus one, or monkey in the middle when adding numbers that are 2 apart, than to practice them over and over. Some of the tricks got a bit weird as I recall (like tall numbers or straight numbers or something). I am sure those tricks are helpful for some kids, but it just made math fact frustration worse for my dd (who gets math concepts easily, but has a hard time spitting out facts quickly).

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Magic 9s:

9+8 = 17 because 7 is one less than 8, then put a 1 in front.

or 9+5= 14 because 4 is one less than 5, put a 1 in front.

 

"Number in the Middle":

6+4 = 10 because 5 is the number b/w 6 and 4 and you double it.

3+5 = 8 b/c 4 is the number b/w 3 and 5 and double it.

 

I think it's nice to have an arsenal of math tricks in you back pocket to help when you need it, but I also don't want to confuse him with too much and cause him to over think about simple addition.

 

If you teach these as "tricks" to memorize and apply, then you are adding a HUGE cognitive load and making math more difficult than it has to be.

 

But if you take time to play with these tricks and see why they work -- like, the reason you use the "one less" number in the Magic 9s trick is because the 9 has taken 1 for itself, in order to become a 10 -- then you are deepening the student's understanding. I still might not want to do too many of the tricks, but I don't think they would be harmful.

 

For instance, can your student see that "Number in the Middle" will work for ANY two numbers you want to add? If you want to add 10 + 20, that is the same as double 15. Or 40 + 60 is the same as double 50. All you are doing is taking the extra amount on the bigger number and sharing it between the two numbers.

 

A lot of Singapore Math word problems will use a similar trick: "May had 70 stickers and her brother Joey had 40. She gave him some stickers, and then they both had the same amount. How many stickers did May give Joey?"

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Thank you everyone for your thoughts! I think I'll continue with the book but I won't emphasize learning the tricks too much. I'll let him try to "see" how it works and then try to deepen the understanding to other larger numbers as suggested so he can understand why.

 

If he takes to them then great! But if he doesn't, well then there are a ton of problems in the book, at least he'll have had a lot of extra practice.

 

Thanks again!!!

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