Bloomberg LP is buying BusinessWeek magazine in a deal that brings together a financial news service specializing in rapid-fire updates with a print publication struggling to adapt to the Internet’s information whirlwind. Terms were not disclosed. The sale announced Tuesday is expected to close by the end of the year. It would end BusinessWeek’s 80-year run as part of McGraw-Hill Cos., which also owns the Standard & Poor’s credit rating agency. McGraw-Hill put BusinessWeek on the auction block in July, apparently fed up with the losses that have been mounting at the magazine as its advertising revenue plunged.