Amazing Math

[Weis1]

You've got to try this... kind of intriguing, any way to explain this?

1. Key in the first 3 digit of your phone number into the calculator.
2. Multiply by 80.
3. Add 1.
4. Multiply by 250.
5. Plus last 4 digit of your phone number.
6. Plus last 4 digit of your phone number again.
7. Minus 250.
8. Divide by 2 at last.

Is this your handy phone number???

[Bond]

No, I'm not the type that pulls wings off flies. BUT...

Let's break this down a little:

Let x = first three digits of phone number
Let y = last four digits of phone number

After step 2, we have 80x.
After step 3, we have 80x + 1.
After step 4, we have (80x + 1) * 250, or 20000x + 250
After step 5, we have 20000x + 250 + y
After step 6, we have 20000x + 250 + y + y, or 20000x + 250 + 2y
After step 7, we have 20000x + 250 + 2y - 250, or 20000x + 2y
After step 8, we have (20000x + 2y) / 2, or 10000x + y

So we're really just adding four zeros to the first three digits, then adding in our last four digits.

i.e.,
x = 123
y = 4567

Using 10000x + y, we get 1230000 + 4567, or 1234567.

(Sorry if I ruined this for anybody. I HAVE to figure stuff like this out).

[Dave420]

and people say you will never use algebra ;)

[Bond]

Well, never for anything that matters, anyway. :)