US employers added more than 240,000 jobs in January, beating economists expectations with the biggest gains in nearly a year, and providing more evidence that the recovery may at last be gathering speed. The hiring surge, which was spread across several key industries, helped push the unemployment rate to its lowest level in the nearly three years, the Labor Department reported yesterday. The jobless rate, which has plunged nearly a point since summer, fell to 8.3 percent last month, from 8.5 percent in December