Zynga, the San Francisco, CA start-up of games FarmVille and CityVille, played on Facebook’s website filed for an IPO (Initial Public Offering) in a deal that values the company at $20 billion.  Zynga, reported net income of $91 million on revenue of $597 million in 2010.  Its revenue comes from the sale of “virtual” goods such as tractors in FarmVille and “energy” in CityVille.

John Deere & Co. manufactures and distributes “real” tractors, loaders, combines and harvesters.  Deere reported net income of $2.5 billion on revenue of $29 billion in 2010.  Its market capitalization as of 7/1/10 was $22 billion, almost the same valuation as Zynga’s.

Hmm!  Must be the new math!  “Virtual” + $91 million net income = “Real” + $2.5 billion net income.

Zynga, is the latest of web start-ups including LinkedIn and Pandora Media to file IPOs seeking to cash in on the appetite for internet companies.