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Hello Linda,
Thank you for your question.
I as understand it. The method taught in Level C is the preferred method to be taught in this program.
The fact is subtracting from right to left (the way we were taught) is not the only way to teach multi-digit subtraction. In fact, many other countries teach their kids to subtraction from left to right.
The concept behind it has some interesting reasons.
First, when we add we add from right to left, and we trade up.
Being that subtraction is the opposite of addition and we are trading down, it makes sense to be going from left to right.
Second reason is, going from left to right you can spot your mistake in the place value column it is in sooner then having to go through the whole problem and doing borrowing.
Third reason is, it shows the child that there is more than one way to solve a math problem.
Fourth reason is, they will be more likely to be able to mentally compute the numbers learning it this way, as they will go from the higher place value to the lower place value.
The following is a note that Dr. Cotter has made for parents where this program is taught in a classroom environment. You may find it helpful.
SIMPLIFIED SUBTRACTION
The children in the second grade mathematics program are learning to
subtract 4-digit numbers. They are using methods that may be new to
you, in which the work proceeds from left to right like division, rather
than right to left like addition. The methods are explained below.
2-Digit Numbers First the children learned to subtract mentally 2-digit numbers. In everyday
life most people do not reach for paper and pencil or even a calculator
for such computations; instead, they do them in their heads.
There are many good shortcuts that can be used; however, a good general
procedure is the following. To subtract 86 – 52, think 86 – 50, which is 36;
then 36 – 2, giving 34. Next try 86 – 57; again think 86 – 50, which is 36;
then 36 – 7, giving 29.
4-Digit Numbers Before the children attempted subtraction on paper, they worked extensively
with written symbols and abacuses to understand the process.
According to research, it is easier for most children to complete the work
for trading, or borrowing, before performing the actual subtracting.
In the following example two trades are necessary.
8572
-6913
First consider the thousands; is a thousand going to be needed for a trade
to get more hundreds. Yes, because 913 is more than 572, 1 thousand will
be traded for 10 hundreds. Indicate it by underlining the 8.
8572
-6913
8572
-6913
Next look at the hundreds; is a hundred needed to make more tens. No,
because 13 is less than 72, a trade is not necessary.
Finally, consider the tens; will 1 ten need to be traded to get 10 more ones.
Yes, a ten is must be traded because 3 is more than 2. Underline the 7 as
shown above.
Now the actual subtraction can take place; 8 thousand – 6 thousand = 2
thousand, but write 1 in the thousand place. See below. Note that the line
under the number indicates subtracting an extra 1. Next 15 hundreds – 9
hundreds is 6 hundreds; write 6. Continue with 7 tens – 1 ten = 6 tens, but
7 is underlined so write 5. For the ones, 12 – 3 = 9.
8572
– 6913
1
8572
– 6913
16
8572
– 6913
165
8572
– 6913
1659
This method simplifies problems with zeroes, such as the following:
4808
– 3457
1
4808
– 3457
1351
8002
– 4567
3
8002
– 4567
3435
Try other examples. Encourage your child to explain it to you.
Some advantages Simplified Subtraction is easier for children to understand and perform.
Note it is possible to calculate any digit of the remainder without going
through the entire procedure. Also, children may be less likely to add for
a subtraction problem because they need to decide where to start.
I want make sure you are clear that this is the way Dr. Cotter will be teaching multi-digit subtraction. I personally, recognize that this is harder for parents to grasp then for the children they are teaching. The children usually struggle when the parents aren’t sure how this method works. I can assure you from personal experience, this was hard for me to become comfortable with it, and found my kids did not struggle as much as I did. I will be teaching my third child this in the next few weeks and can finally tell you, I get it! It did not come easily I worked to see the sense in it. So I know if I struggled, and I am a regular mom like everyone else, I am sure many others struggle with, “Why this way?” “How long are we to do this?” and “Can’t I just skip it?” but I would encourage you to give this a try and see if it develops into an easier way of subtraction.
If you are more curious, Wikipedia has an interesting article about subtraction.
http://en.wikipedia.org/wiki/Subtraction (Copy and Paste)
Look under the title “Algorithms for Subtraction” it has some more information about the different types of multi-digits out there.
Please let me know how it works out, and give us a call at 888-272-3291, or email me if you have more questions.
Thank you for giving your child a RightStart in Math!
Carissa
Customer Service Rep
RightStart™ Mathematics by Activities for Learning, Inc.
For program questions: 888.272.3291
To place an order: 888.RS.5.MATH (888.775.6284)
www.RightStartMath.com
Our Mission: To help children understand, apply, and enjoy mathematics
PS I tried my best to get the numbers in the equations lined up. I can email you a better copy if you are interested.
Hello Captuhura,
That is correct! 
That is one of several ways you can see that you need to trade, but that is by far the easiest way to see it, well that's my opinion.
Thank you for giving your child a RightStart in Math,
Carissa
RightStart™ Mathematics by Activities for Learning, Inc.
For program questions: 888.272.3291
To place an order: 888.RS.5.MATH (888.775.6284)
www.RightStartMath.com
Our Mission: To help children understand, apply, and enjoy mathematics
