India.
http://wiki.answers.com/Q/Where_did_the_number_zer...

1. Set a timer for 5 minutes and count as quickly as you can until the timer signals the 5 minutes have expired. Take this number, no matter how high or low it is, and use long division
http://www.ehow.com/how_2054935_knownumberdivisi...

It's not so much the inclusion of zero as it is the use of a positional numbersystem, like our modern base10 one. The Maya were using base 20, and had a relatively simplistic way
http://www.quora.com/HistoryofScience/Whatisth...

1. Let two numbers be A and B. Ad. 2. Assume A = B, thus A + B = 2A. 3. Subtract 2B from each side. You get A + B  2B = 2A  2B. 4. Factor the 2 out of the right side. You get A
http://www.wikihow.com/KnowifaNumberIsDivisib...
