A hiker walking at a constant rate of 4 kilometers per hour is passed by a cyclist travelling in the same direction along the same path at a constant rate of 24 kilometers per hour. The cyclist stops and waits for the hiker 5 minutes after passing her while the hiker continues to walk at her constant rate. How many minutes must the cyclist wait until the hiker catches up?
Pick one.
A) 10  B) 15  C) 20  D) 25  E) 30

Rationale: "in 5 minutes , the cyclist travels a distance of ( 5 / 60 ) * 24 = 2 km . the time it takes the hiker to complete this distance is 2 / 4 hours = 30 minutes the cyclist needs to wait 30 - 5 = 25 minutes the answer is d ."
Answer: D