Thread: The Borrow Later Method of subtraction.

1. The Borrow Later Method of subtraction.

This website is created to show a different way to subtract when borrowing (regrouping) is required.

The site is at www.borrowlater.com and it's a free education site that I have created.

Since everyone has to subtract, it is useful for any age.

I would love to have some math geeks take a look at it and let me know what they think of the idea.

Thanks!

2. Originally Posted by Borrow Later
This website is created to show a different way to subtract when borrowing (regrouping) is required.

The site is at www.borrowlater.com and it's a free education site that I have created.

Since everyone has to subtract, it is useful for any age.

I would love to have some math geeks take a look at it and let me know what they think of the idea.

Thanks!
I don't like it.

The method at the beginning is the standard way to subtract, and it is taught that way because it reinforces the concept of place value, in other words "that 2 tens is 20 ones" or "6 thousands is 60 hundreds", etc. The borrowing from columns then becomes a natural extension. It can also be taught using concrete objects to benefit kinaesthetic learners.

This "borrow later" method, while it may work, has the appearance of being created at random and gives no explanation why it works.

Also, I don't like how it says $\displaystyle 5^{-1}$ is the same as $\displaystyle 5 - 1$.

These are NOT the same thing, and will cause confusion to students when they begin working with indices. And since the purpose of this site was to avoid confusion, it seems like a circular argument to me.

3. > and it is taught that way because it reinforces the concept of place value, in other words "that 2 tens is 20 ones" or "6 thousands is 60 hundreds", etc.

It wasn't the intent to change the meaning of this section. The problem still requires the "2 tens is 20 ones" concept but just at a different time. We still 'borrow' from the tens column. I may need to adjust the explanation of it.

> Also, I don't like how it says is the same as .

I completely agree with this observation. I've struggled on how to make this part more clear.

I've considered $\displaystyle 5^{-}$, $\displaystyle 5^{'}$, and others but I never came up with a more useful notation.

Although negative, I do appreciate your response!