Amusing math trick.
 

Grab a calculator. (you won't be able to do this one in your Head)

1. Key in the first three digits of your phone number (NOT the Area code)
2. Multiply by 80
3. Add 1
4. Multiply by 250
5. Add the last 4 digits of your phone number
6. Add the last 4 digits of your phone number again.
7. Subtract 250
8. Divide number by 2

Do you recognize the answer ??

What do you mean I can't do that in my head? Speak for yourself.

Sorry jeenyus. :D

thats cool!

if your phone number is abcdefg for some digits {a,b,c,d,e,f,g}, the equation comes out to:

(((80*abc + 1)*250)+2*defg-250)/2
= (80*250*abc + 250 +2*defg-250)/2
= (20000*abc +2*defg)/2
= 10000*abc + defg
= abc * 10^4 + defg
= abc0000 + defg
= abcdefg
= your phone number

There's nothing interesting about this. A gradeschooler could invent the steps to get this result, as it's all based on (80 *250)/2 = 10000.

I said amusing. I didn't imply that it was some life changing, supremely difficult math problem. It is pointless, and it is easy, but I have not seen it before and was amused. Sorry if you found that it was beneath you.

Would punching 58,008 into your calculator and then turning it upside down qualify as a math trick?

I asked my wife. She hit me!! :laugh

Yes. That's a classic from waaay back in the day. :D

If you take a convolution integral, you can LaPlace transform the arguments, add them together, and inverse LaPlace transform them, and the result is the product of the convolution arguments.

Now that's a sweet math trick.

$

My favorite math trick so far is either using the heat equation to value a future option or using modular arithmetic on large numbers to encode a message into an uncrackable code (RSA).

Pointing out to mav fans that 3 > 0 is another math trick I find quite entertaining.

Yep. Give any puberty stricken teenage boy a calculator and he'll have derived that magic numerical sequence in a matter of minutes.

But I did it in my head :bs :D

Good for her! :nope Men truly are from Mars. :D

Maybe you should have them type in 7734206 instead.:evil

I don't know if that's a trick so much as the purpose of the Laplace Transform.

Did you know that 142.857 is a curious number?

142.857 x 2 = 285.714 ( same digits )
142.857 x 3 = 428.571 idem
142.857 x 4 = 571.428 idem
142.857 x 5 = 714.285 idem
142.857 x 6 = 857.142 idem
142.857 x 7 = 999.999 !!!
142.857 x 8 = 1.142.856 (number missing is 7, but last -6- and first -1- add to 7
142.857 x 9 = 1.285.713 (number missing is 4, but last and first add to 4 )

You can go on and on...

:elefant

:D

This one is the key to all that. Multiples of 9 produce a lot of odd number things.

Remember the way the whole 9 times table added up to 9?


:elefant