Voltage Multiples of 11? Voltage Multiples of 11?

hi friends...
last three days,.I am away from my home place for my office work ..so,I am very busy with it..
know i am back to blogging..

today my brother asked me a question,who is studying +2, that why all voltages are multiples of 11 only as 110v,220v,440v,11KV,132KV..., As i am an electronics and communication engineer didn't able to answer it,even i never got such question during my course.....

immediately opened the screen of Google and started searching ..i did for a half hour but i didn't find the exact reason for it..may be no reason for it..i don't know at present.

here i am posting some of interesting forum discussions on this topic. If any one knows exactly please comment on this post...

http://cr4.globalspec.com/thread/3861/Voltage-Multiples-of-11
http://www.allinterview.com/showanswers/32841.html
http://in.answers.yahoo.com/question/index?qid=20080719115118AAl6YhK