Car A is chasing car B, and the respective speeds of the two cars are fixed. If car A chases at twice the current speed, it takes 5 hours to catch up; if car A chases at three times the current speed, it takes 3 hours. Can catch up; if car A chases at the current speed, how many hours can it catch up with car B?
甲车追乙车，两辆车各自的速度固定，如果甲车以现有的速度的2倍去追，5小时可以追上；如果甲车以现有的速度的3倍去追，3小时可以追上；若是甲车以现有的速度去追，几小时可以追上乙车？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / (1/15) / 1</gadget>
<output>15</output>

<result>15</result>