There are three circular runways, the centers of which are all at the flagpoles in the playground. The inner runway is (1/5) km long, the middle runway is (1/4) km long, and the outer runway is (3/8) km long. A, B, and C run in the same direction in the inner circle, middle circle, and outer circle respectively. At the beginning, all three people are in the east direction of the flagpole. A runs 3 (1/2) kilometers per hour, and B Runs 4 kilometers per hour, and C runs 5 kilometers per hour. They set off at the same time. I would like to ask: How many hours later, the three returned to the starting point at the same time for the first time?
三条圆形跑道，圆心都在操场中的旗杆处．里圈跑道长(1/5)千米，中圈跑道长(1/4)千米，外圈跑道长(3/8)千米．甲、乙、丙三人分别在里圈、中圈、外圈沿同样的方向跑步，开始时，三人都在旗杆的正东方向，甲每小时跑3(1/2)千米，乙每小时跑4千米，丙每小时跑5千米．他们同时出发．请问：几小时后，三人第一次同时回到出发点？
<gadget id="calculator">3_360 / 560</gadget>
<output>6</output>

<result>6</result>