The question addressed Obama's father, Obama Sr.

Obama Jr's mother was white.(50%)

Obama Jr's father (the other 50%)was 7/8's Arab and 1/8 Negro

Result: the candidate is 50% white, 44% Arab and 6% Negro (All of which would be irrelevant if he were not running as a black)

Siince posing the question I googled the subject and refer you to

http://kennethelamb.blogspot.com/2008/02/barak-obama-questions-about-ethnic.html

and to http://thepeoplescube.com/red/viewtopic.php?t=1916.

As to the last site, please note that Obama's ancestors were enslavers not slaves.

Thanks for taking the time to ask the question.