A small Math trick for small kids

Dont know if its the right forum to post this!! Also if you have patience please read it.

I got this piece of trick from my dad, while i was young. Its about telling the number u have imagined by asking some one to do some simple calculation and getting the 'indirect' intermediate result. Some of you may be knowing this already, but it was a fun during my school dayz and i used to play this with my class mates.
It goes like this
1.Ask a person B to imagine any number(he imagined 3).
2.Ask him to multiply that number by 3( its 9 now)
3.Ask him to divide the above result by 2 (its 4.5 now)
4.Ask him if the result contains decimal places (its 4 now)
5.Ask him to remove the decimal and multiply by 3(its 12 now)
6. Ask him to divide that number by 2 again (its 6 now).
7.Now again ask the result from step 6 has decimal places in it
8.Also ask how many times u can divide it by nine.

Now how u will come to know about the number the person b has imagined.
The Questions in step 4, 7 and 8 will help you to find that.
if he got deciaml places at steps 4 and 7 u shud consider 1
if he got decimal plces in 4 only then u shud consider 3
if he got decimal places in 7 only u shud consider 2
Now the above number has to be added with 4 X number of times divisible by 9.
I will consider the case when the other person imagined 9.
2. 9 X 3= 27
3. 27 / 2= 13.5
4.the result has decimal (so consider 3)
5.remvoing decimal and multiplying ( 13 X 3= 39)
6.Divide it by 2 = 19.5
7.its divisible by 9 twice
So the number he imagined would be
1 (since he got decimals twice)+ 2 (since its divisible by 9 twice) multiplied by 4
which is 1 + 8= 9, which is the original number