BVC-CHAT tricky math

[drjinx at texas.net]

Not that this has anything to do with bicycling, but
in case anyone hasn't seen one of these schemes unpacked,
all it is doing is have you do some operations to a number
then undo them.  No magic required....

> Ok, this is cool.  How does it work?

Your phone number is d1 d2 d3 d4 d5 d6 d7 e.g. 8 3 7 5 3 0 9

> Using a calculator:
> 
> Enter the first three digits of a phone number, not the area code.

(enter (d1 d2 d3 d4 d5 d6 d7)/10000 truncated to an integer 
= d1 d2 d3 = (d1 d2 d3 0 0 0 0)/10000) 

note that 837 = (8 3 7 0 0 0 0)/10000
 
> multiply by 80
>
> add 1

80*(d1 d2 d3 0 0 0 0)/10000 + 1 

80*(8 3 7 0 0 0 0)/10000 + 1

> multiply by 250

= 250*[80*(d1 d2 d3 0 0 0 0)/10000 + 1]

= 2* 10000*(d1 d2 d3 0 0 0 0)/10000 + 250 

= 2(d1 d2 d3 0 0 0 0 ) + 250

note that this is 2*(8 3 7 0 0 0 0) + 250 for our example number

 
> add the last four digits of the phone number
 
> again, add the last four digits

You get 2(d1 d2 d3 0 0 0 0) + 2*(d4 d5 d6 d7) + 250 =
2(d1 d2 d3 d4 d5 d6 d7) + 250

in our example: 2(8 3 7 5 3 0 9) + 250

> subtract 250

= 2(d1 d2 d3 d4 d5 d6 d7)

in our example 2(8 3 7 5 3 0 9)
 
> divide by 2

= d1 d2 d3 d4 d5 d6 d7

in our example 8 3 7 5 3 0 9

> The number on the calculator screen will be the phone number.

Just like magic, huhn?

"Jenny, I've got your number ... I wanna make you mine!  Jenny don't change
that number ... 8 3 7 5 3 0 9"

Jean Marie aka Tommy Tutone