Today in my Mathematics, I learned about algorithms for subtraction. I learned that there are 2 methods and then 2 alternative methods for those students who might be a little advanced. Just like with addition, there are Visual and Expanded Notation.
With the visual for subtraction, again, you can use base-ten blocks.I'm starting to realize that with elementary students, base ten blocks are going to be my best friend when it comes to teaching to math.
So an example of visualization would be, 24
-17
Expanded notation is when you write the equation in words. For example,
24
-12
I would write that as: 2 tens and 4 ones
-1 ten and 2 ones
Which equals: 1 ten and 2 ones
After this step, I would write this problem:
1x10 + 2x1=
10 + 2= 12
http://math.about.com/od/addingsubtracting/ss/2DigitSubNR.htm
