The number trick, help me please

I want to know the number trick, were they tell you pick a secret number, then multiply it by 2, then throw half of your number in the sea, then add 5 and deduct the number you picked in the first place or sumthing like that, how do you know the number...

you though of??? every time its a diff number

Why Don't you try diff numbers To subtracy and divide?

I dont know it, I want the secret of it

It's just a sequence of math operations that will always give the same result. Yours would always result in -5, if I'm reading it right.

no, a human being will tell you that trick, not math sequences, and the number is always diff but correct