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Well, a couple of them, actually.
First one:
Think of a number.
Now double it.
Now add 10.
Now divide by 2
Now subtract from your original number
Answer: 5.
Second one:
take any three digit number, where all three digits are different (i.e. 123).
Now, reverse and subtract the smaller from the larger (i.e. 321 - 123)
Take the answer, reverse it, and add (i.e. 321 - 123 = 198, so 891)
Take that number, reverse it, and add them together (i.e. 891 + 198)
The answer is 1089...
In step two, if you end up with a two digit number, add a zero onto the end after you flip (i.e. 89 would turn into 980).
Also, did you know that the difference in a number transposition is a multiple of nine?
Consider the number 50394
Now, if you accidentally write 50934, that's a problem.
but watch this: 50934 - 50394 = 540
and 540 / 9 = 60
First one:
Think of a number.
Now double it.
Now add 10.
Now divide by 2
Now subtract from your original number
Answer: 5.
Second one:
take any three digit number, where all three digits are different (i.e. 123).
Now, reverse and subtract the smaller from the larger (i.e. 321 - 123)
Take the answer, reverse it, and add (i.e. 321 - 123 = 198, so 891)
Take that number, reverse it, and add them together (i.e. 891 + 198)
The answer is 1089...
In step two, if you end up with a two digit number, add a zero onto the end after you flip (i.e. 89 would turn into 980).
Also, did you know that the difference in a number transposition is a multiple of nine?
Consider the number 50394
Now, if you accidentally write 50934, that's a problem.
but watch this: 50934 - 50394 = 540
and 540 / 9 = 60