Pick a # between 1-10. (Don't tell me)

Double it

Add 6

Cut it into half

Subtract it from the # you started with

Is your answer 3?

I can do this all day long :)

Ask me others if u want

Obviously... =)

 Your number = #

(2# + 6 )/2 -# =

 #+3 - #=

=3 

You could choose any number (that includes numbers like pi or square root of 2 or even a+bi (complex numbers))

 Here is one a little harder.

Take any natural number (from 1 to infinity).

 1. Divide this number by 2 until you get an odd number, go to step 2.

2. multiply by 3 and add 1

Repeat step 1 

 In the end you will always get the same number, what is it?

It is conjectured that you will always eventually get to 4, but it yet to be proven. A paticularly long example of is 27, which gets up to the thousands before reaching 4.

I see where you are coming from, if you actually stop at step 2, you will end up to 4, but since 4 is divisible by 2, twice, you will get back to 1. I prefer to say it ends at 1.

Yes 27 will get pretty high numbers before it actually gets to 1 (or 4).