Two boats are heading towards each other at constant speeds of 4 miles/hr and 20 miles/hr respectively. They begin at a distance 20 miles from each other. How far are they (in miles) one minute before they collide ?  Pick one:
A) 1 / 12  B) 6 / 15  C) 1 / 6  D) 1 / 3  E) 1 / 5

Rationale: "the question asks : how far apart will they be 1 minute = 1 / 60 hours before they collide ? since the combined rate of the boats is 4 + 20 = 25 mph then 1 / 60 hours before they collide they ' ll be rate * time = distance - - > 24 * 1 / 60 = 6 / 15 miles apart . answer : b ."
Answer: B