place value

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  • March 3, 2011 at 6:28 pm
    nerakr
    Participant

    Ds7 (end of year 1) is beginning to add and subtract two-digit numbers. I tell him he needs to start with the number on the right, but he doesn’t want to. We are not carrying and borrowing yet. I have not explained place value to him. At the beginning of the school year he could construct high numbers with a place value game I had, so I wasn’t sure it was necessary. But now I’m wondering if it is. How else can I explain carrying and borrowing when I come to it?

    I’m not using a formal math curriculum, so I don’t have a teacher’s manual to refer to on this.

    TIA,

    Karen

     

    March 3, 2011 at 6:41 pm
    Scherger5
    Participant

    Do you have some play paper money (100’s, 10’s, and 1’s)?  It helped my son understand the concept better.  It might just be an age thing.  Sometimes when a concept doesn’t click it just means we need to wait and pull it out again later.  Carrying and borrowing is pretty abstract.

    Blessings,

    ~Heather

    March 3, 2011 at 6:48 pm
    LindseyD
    Participant

    Karen,

    Math-U-See does a great job of explaining place value. There is a poster with what they call Decimal Street on it. There is a units house, a tens house, and a hundreds house. Only nine members are allowed to live in each house before the tenth one has to move in next door. It is a great, tangible way to help kids see that every number has a place and a value and that we always start with units (on the right) first.

    Is that what you’re asking?

    Lindsey

    March 3, 2011 at 6:59 pm
    nerakr
    Participant

    I’m not asking how to explain it. The math workbook we’re using has a lot of pages on place value, so explaining it shouldn’t be a problem. I’m just wondering if it’s necessary or if I can explain carrying and borrowing without it when the time comes.

    March 3, 2011 at 7:31 pm
    Wings2fly
    Participant

    Yes, it is necessary.  I am familiar with both MUS and RS.  MUS starts the very first lesson of Alpha with place value.  You have to master that before going on in their lessons.  In the RightStart lessons, they also want the child to master this before moving on and they recommend spending 3 days on that lesson #8 (instead of 1 day).  I really like the place value cards from RS.  We use them along with MUS decimal street.  There are cards 1 to 9 for units.  10, 20, 30, 40, 50, 60, 70, 80, 90 for the tens.  100-900 of the hundreds in the same manner.  So if your number is 358.   You would use the following cards: 300, 50, 8  The 8 covers up the 0 in 50 and the 58 covers up the 00 in 300.  It helps for them to be able to see the big number 358 broken up.  Then they know the 3 is not really 3, but 300 hidden under the other numbers.  You can make your own place value cards to use.  I think you would need to have 358 of something to count with them.  Otherwise, it would be too abstract.  You could use 3 packages of 100 cotton balls and another package you count out the 50 and the 8.  Yes, we have counted all the way through 300 just to make a point.  I hope that helps answer your question.

    You could also do two digit adding with cards like this to make your point of carrying the value over 9.

    March 3, 2011 at 7:32 pm
    Sara B.
    Participant

    I would start with the concrete, honestly.  Just explaining it, he may or may not get it.  Or, worse, he may know *how* to do it, but not *why* which is how I was taught all through school.  I watched the MUS demo last week, and it really opened my eyes to WHY we do such-and-such with a math problem.  And I am a whiz at math!  LOL  Carrying and borrowing are definitely something my children have to see to get.  There’s a reason you’re carrying and borrowing from different places, and seeing it and visualizing it has helped my oldest (finishing 2nd grade soon) really comprehend the “why” behind the way we do math.  We aren’t using MUS this year (BJU right now), but I am nearly sure we will be switching to MUS for next year.  We all need something more concrete to visualize this place value stuff.  It really is the basis for all of math, from adding and subtracting, to multiplying and dividing, to algebra and exponents, etc.

    March 3, 2011 at 8:43 pm
    nerakr
    Participant

    I pulled out the place value file folder games I used briefly earlier in the year. Tomorrow I plan to use those along with the markerboard and see if that helps. I don’t have any Unifix cubes, so if that doesn’t work I may be gluing beans onto sticks or grouping toothpicks with rubber bands. But I’ll definitely be doing something. Thanks for the advice.

    March 3, 2011 at 9:50 pm
    Sue
    Participant

    Both of my younger children, 10yo and 11yo, “don’t want to” start with the “ones column” for some reason.  Perhaps it is because, over the past several years of teaching them to read, we have been gently instilling in them the habit of starting at the left and moving right.  Now, here comes addition, and we expect them to automatically adjust to starting right and moving to the left as you go!  Without introducing the concept that “place value” exists, there is no reason (in their minds) to accept this change.

    There is a website (link below) that my son likes that shows groups of hundreds, tens, and ones, and you can use a “hammer” to break them apart into smaller units.  It might bring your child around to accept the idea of place value, and seeing how it works might convince your son to get into the habit of starting to add/subtract with the ones column.

    http://ejad.best.vwh.net/java/b10blocks/b10blocks.html

    Sue

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