>>On 23 Feb, jhobbs wrote:
>/I once knew a fast trick for divide by 3, but now I am unable to reproduce
>>/it.  If someone can share it with me (and others) that would be great.
>>/
>>/Take care -Jim

>>    Simple.  To multiply by 3, double and add to original.  To divide by 3,
>>just do the inverse!
>>-- Mel Evans

>Could someone unfold that for a binary math newbie, please?
>/Morgan
>/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \ \
>mrt@iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

Sure.

Let's start with the number 5. In binary that is:

 101

Since the place value of binary is two, you can double the number by shifting it
left one bit, like this:

Old:  101
New: 1010

Now you add it to the original number, like this


     1010
   +  101
   ------
     1111

The result is the number 15, which is the answer to 5 * 3!


Later,

Eric