Using a bit of clever math, app maker and market analyst firm Asymco has determined that about 38 percent of all 120 million reported iOS device sales are iPod Touches.

The company got the value by subtracting the 59.6 million iPhones and 3.2 million iPads sold through June (figures presented in Apple’s SEC filings) and the estimated July and August iPad and iPhone sales of 12 million — a combined 74.8M iPads and iPhones sold to date — from the 120 million total iOS devices that have been sold to date. The 120 million figure was announced in Apple CEO Steve Jobs’ seemingly annual presentation of new Apple gear on Wednesday.

Jobs said the iPod Touch had become the number one mobile gaming platform — above the Nintendo DS and Sony Playstation portable — during the same presentation. Apple sold 9.41 million iPods in the quarter ending June 26.

It looks to be in an even better position to advance into the portable gaming market with some new hardware. The new iPod Touch boasts Apple’s A4 processor, as well as a gyroscope, and front- and rear-facing camera. Apple will also release iOS 4.1 sometime this week, which brings the Game Center — a multiplayer gaming platform for iOS — live.