A car going 60 miles per hour set out on a 400-mile trip at 12:00 P.M. Exactly 20 minutes later, a second car left from the same place and followed the same route. How fast, in miles per hour, was the second car going if it caught up with the first car at 2:00 P.M.?

Answer 1

the first car went 20 miles before the 2nd car started out.

So, it made up 20mi/(5/3 hr) = 12 mi/hr
That is, car 2 was going 12 mi/hr faster than car 1, or 72 mi/hr

Check: car 1 went 120 miles in 2 hours
car 2 went 72(5/3) = 120 miles in 1 hr 40 min