a hiker walking at a constant rate of 4 miles per hour is passed by a cyclist traveling in the same direction along the same path at a constant rate of 20 miles per hour.the cyclist stops to wait for the hiker 5minitues after passing her , while the hiker continues to walk at her constant rate.how many minitues must the cyclist wait until the hiker catches up? 答案是20 我觉得我没看懂题~~痛苦