Bob drove for one and a half hours at 60/mph. He then hit construction and drove for 2 hours at 45/mph. How many miles did Bob travel in those 3 and a half hours? Let's think first. Chain of thought:
Bob drove for 1.5 hour * 60 / mph = 90 miles. Bod drove for 2 hour * 45 / mph = 90 miles. In total Bob drove 90 + 90 miles = 180 miles.
Therefore, the answer is 180.