Teaching Borrowing in Subtraction

Date: 03/12/97 at 22:52:28
From: S. K. Anania
Subject: Second graders and 2-digit subtraction

I teach second grade.  Some students are becoming very frustrated with
the concept of tens and ones when regrouping.  I'm sure they haven't 
grasped tens and ones but I'm forced to move on.  What kind of 
remedial suggestions do you have?  We have been on manipulatives. I do 
have students explain their methods.  We demonstrate on the overhead. 
I have imformed parents.  Yes, these are some of the same students who
don't readily know their basic facts. I appreciate any suggestions.

Date: 03/14/97 at 11:15:09
From: Doctor Barney
Subject: Re: Second graders and 2-digit subtraction

Get several boxes of toothpicks and lots of those twist-ties used to 
keep plastic bags shut.  Give students between 11 and 99 toothpicks 
each and have them tie up bundles of ten toothpicks. Explain that the 
number of bundles is the tens digit, and the number of loose 
toothpicks is the ones digit.  

Now ask them to give you back (subtract) a number which requires 
borrowing. When they have to unbundle one of their sets of ten 
toothpicks the concept should be a little clearer.  

May your patience be rewarded with enlightenment.

-Doctor Barney,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/