Two trains 420 miles apart travel toward each other at 70 and 50 miles per hour. How long until they meet?

Correct answer to question 82 (Arithmetic Reasoning): 3.5 hours

Method

Approaching objects close the gap at the sum of their speeds, 70 + 50 = 120 miles per hour, so 420 / 120 = 3.5 hours. Using one speed alone gives 6 or 8.4 hours.