calculator trick

[Seawood]

i have seen this trick alot and i have even heard it mentioned in this forum before but i want to know were i can learn it.
the trick is where a borrowed calculator is used (normally a spectators phone) the phone is handed to someone they put in a random number. the phone is handed on and the same thing is repeated a few times with the numbers either being added or multiplied together. The number is then either a phone number or the days date (a obviously predetermined number) can anyone tell me where to learn this or where its from.
thanks for your time
Seawood

 

[Viper12]

I think that effect can be found on the dvd -This is Mentalism- by rich ferguson.

great trick!

 

[pokili12]

This is mentalism - rich ferguson

 

[Bending the Real]

The only calculator trick I know of, is where you have someone type out 5318008 and turn it upside down

 

[5Aces1010]

How is this relevant to cardistry/flourishes?