JJ's New Math Skill--Carry Over Subtraction

Recently I got a set of wooden number rods (similar to the Montessori Number Rods, only in different colors and fit in a child's palm) at a sale for $1.  I write numbers on them to identify their lengths.  Then, I use them to introduce the concept of carry over subtraction to JJ.  Here's how:

1. Set the minuend (the number that is to be subtracted from) using number rods.  In this case, 15--1 ten rod and 1 five rod.
2. Since the subtrahend (the number that is to be subtracted) is greater than the one's place of the minuend, JJ needs to substitute the ten rod with 10 ones cubes. 
3. Remove the ten rod.
4. From the 10 ones cubes, subtract the subtrahend.  In this case, 6 ones cubes.
5. Remove the cubes and get the difference.  Start by saying the name of the number rod (5), then add the remaining ones cubes to that number (6, 7, 8, 9).  Easy?  JJ thinks so, too.

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JJ's 2nd Abacus Lesson--Free Download/Printable

You could download and print the Number to Beads Worksheethere.

 

You could download and print the Beads To Number Worksheet here.

 

Funny that while I was working on those worksheets, JJ was busy reproducing her version of the abacus blank worksheet.  Well done, baby.

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JJ's 1st Abacus Lesson

I was surprised to hear Z said that learning abacus years ago had helped him with visualizing numbers in his head.  His comments motivated me to get JJ started learning abacus.

The 1^st lesson was to learn how to hold the abacus and pen, the basic movement of beads, and to notate the beads.  I drew 10 squares in a row to have JJ notate 1-10 as she moved the beads one number at a time.

At the end of the lesson, this is what she had.  Good job, JJ!

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