A driver travels 150 miles at 50 miles per hour, then 90 miles at 30 miles per hour. What is the average speed for the whole trip?

Correct answer to question 174 (Arithmetic Reasoning): 40 miles per hour

Method

Average speed is total distance over total time, not the average of the two speeds. The legs take 3 hours and 3 hours, so 240 miles over 6 hours gives 40 miles per hour.