Think of a number from 1 to 10.
Double it.
Add 12
Half it.
Take away the number you first thought of.
And you have the number 6 in your head.
No, I'm not telling you how I do it.
I had this stupid thought, by doubling the original number you are ensuring that the result is an even number, let's say 3 doubled is 6, then you are adding 12, so we have 6+12, then you halve the total which can also be shown as 3+6, by then taking the original number away [3] you are left with 6, or half of 12. But that would be too easy wouldn't it?