Tuesday, May 7, 2013

Mental math with addition.

I have been very lucky to understand how to do arithmetic mentally, but maybe some people haven't been as lucky.  Here is a simple example for a young child to understand an addition problem.  By the way, mental math really only involves thinking about the nearest 5 or nearest 10.

Say we have the problem 7+8=
When we look at a group of objects, our eyes tend to group things into small groups, normally 2 and 3.  We also tend to sort things by color.  Looking at this group, mentally I would separate it as 3+2 blue is 5, 2 green, 3+2 pink is 5, and 3 gold.  It would look like this...
Knowing how to add 5s is really easy so we group those together--and addition is fun because we can easily move the numbers around (Commutative Property).  Our problem then becomes this.
And we see that it is just 5+5+5 which is 15.  Then if your child is ready you can show them they can do multiplication with this one...

Mental arithmetic can become easier if you practice and just think about how close the digits are to an easier number to work with.  For example 63+19: Separate into 60 and give the 3 to the 19 to be 22 and now the problem is 60+22.

I hope you enjoyed the addition mental math session!

How are you when it comes to doing arithmetic?  Can you do it mentally or do you need to write everything down?  Or do you pull out a calculator?

5 comments:

  1. Awesome, your comment thing is now fixed. Now can you tell me how you fixed it. I'm trying to help others. Mental math and grouping is something I never learned in school. Both DD and Hubby, the accountant did. I've learned a bit from them, and find I've improved my ability to do mental math...or at least a combination of. Like doing part mentally and then perhaps writing it down after you've figured out a portion or two of it, in order to remember the actual numbers. The later, perhaps is a bit of an age thing, lol.

    Happy to be able to get to your blog again, glad you left the link to your blog vs your google+ page. and even better being able to leave a comment.

    Looks like you're growing nicely, congrats on that. I've stirred clear of the google+ because of the these issues, and have read it hurts your google ranking elsewhere; but then a few days ago read it helped with the new algorithms. So, it seems there are multiple opinions as to how helpful it is. Do you have a feel yet whether it's helped you? Would consider signing up if I could avoid the issues you've addressed.
    Sandy

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  2. I like this for teaching my kiddos, thanks! I do tend to change numbers up to do mental math. Once it became a natural thing to do, it got so much easier.

    Shannon at The Warrior Muse

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    Mental Arithmetic

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  4. Well, mental math helps lot in calculation. Anyway, great article. Keep it up, the way you blog is remarkable.

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Thanks SO much for stopping by! I appreciate your comments and any ideas you share! Have a wonderful day : )

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