Here is the video I made: http://www.youtube.com/watch?v=Kk9U_pGvLU0]]>

it was funny because I had forgotten he taught me that, so this morning

I redeveloped the same method with the increment on the bottom for the

carry, and showed it to my mom. She thinks I came up with it, but really

it was luca-d that did!!!!]]>

Reaction Math would probably improve your mental arithmetic skills, then.

]]>12345-6789

= (+6000)-444

= 5556Using my method this would only take a second or two...

youre method is the way i usually would do these sort of things in my head, but when its something thats not so easy i would have to write it down on paper, im not too good with mental arithmetic

]]>Hope you like the method.

]]>One typo in answer of #3, perhaps edit it.

Thanks for the lesson ]]>

1098-772

(772+300)+26

1098-772 = 326

---

Example 2;

5897-2653

(+3000)+200+44

= 3244

Example 3:

2097152-524288

(+1500000)+(73000)-136

= 1572864

The 136 was subtracted from my answer because I went over.

]]>Don't even try to explain, but a bunch of numbers would be helpful.

Your method looks quite interesting, and obviously fast.]]>

= (+6000)-444

= 5556

Using my method this would only take a second or two...

]]>12345

- 6789

______

5 from 9 is 4, swap for 6 due to 10 sum.

4 from 8 is 4, swap for 5 due to 9 sum.

3 from 7 is 4, swap for 5 due to 9 sum.

2 from 6 is 4, swap for 5 due to 9 sum.

1 minus 1 is 0, we are done, based on luca.

So answer is 05556.]]>

Another example;

12253-591

=591+10000+1500+162

Occasionally I might do it a different way. But I have been able to tackle every subtraction problem so far with this method.

For 12253-591, rather than using my method I would just do:

(12253-600)+9

= 11662.

]]>mathsyperson wrote:Seriously? You'd start at 123 and count until you got to 456? That would take you ages and be fairly pointless, considering the triviality of the sum. I'm probably misunderstanding you. Any other way though, and you'd have to do it in more than one step.

A bit like number lines. For 456-123, I would do: 123 + 300 + 33.

Hard to explain.

Now I think I get it to give another example:

521-214

you'd do:

214+300+7= 521

so the difference is 307

]]>Seriously? You'd start at 123 and count until you got to 456? That would take you ages and be fairly pointless, considering the triviality of the sum. I'm probably misunderstanding you. Any other way though, and you'd have to do it in more than one step.

A bit like number lines. For 456-123, I would do: 123 + 300 + 33.

Hard to explain.

]]>I know I really should do it the proper way, it's becoming a bad habit now. ]]>