Tuesday, April 22, 2014

R for regrouping (A to Z challenge)

Regrouping!  Sometimes it goes by other names but this is a term often used in subtraction.  Borrowing is also a common name for it.  Both are appropriate.

The word regrouping would mean putting the numbers in different groups.  In the problem below I am regrouping the number 22 to be 10 and 12, but since the 1 is in the tens place you just write the digit 1.

Borrowing is when you think of each digit in their place.  The ones place borrows from the tens place...

It's nice to know how to do problems on paper, but mental math shouldn't be discounted since it is much faster (but I know some teachers can't stand it because there is no 'work' shown).  But how to mentally think of this problem is you have 22 and since 9 is close to 10 you know 22 minus 10 is 12, but it was only minus 9 so you have one more than that, 13.

Which way is your favorite way to solve problems with 2 digits--writing it down or doing it mentally?

4 comments:

  1. Nice and easy, thank you. My son, (4th grader) does it mentally now, but there was a time when this came in very handy.
    Best,
    Silvia @
    SilviaWrites

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    1. Thanks for stopping by! It's great when kids are able to understand concepts well.
      ~Lucy

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  2. I've never heard the term regrouping before.

    It wasn't until I've gotten older that I started doing more 'mental' math. My son is in 4th grade. Math isn't his strong subject but he does okay. I'm trying to help show him how to do things like this in his head.

    But it's like he looks at a problem and just gets overwhelmed and doesn't even try to break things down how you did above. It might seem like more steps but it allows you to do it faster sometimes.

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    1. Thanks for your comments. I hope there are some helpful things on my blog for you to use with your son. I think my best advice is to try and make math fun (just like any kind of learning). It may be possible he has slight bit of dyscalculia. I have a post about that previously you can reference from a mother with a more severe case.

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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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