1 + 1 = 3?

InfoWorld: "On Feb. 25, 1991, during the first Gulf War, a Scud missile hit U.S. Army barracks in Dhahran, Saudi Arabia, killing 28 U.S. soldiers. The barracks was defended by a Patriot missile defense system, which for some reason failed to track and intercept the incoming Scud. A year later, a U.S. General Accounting Office (GAO) investigation into the Patriot's failure concluded that the battery's weapon control system suffered from a fatal flaw: It was bad at math."