A passenger travels by train at a speed of 15 meters per second, and he sees a train coming from the opposite side passing him in only 2 seconds. If you know that the oncoming train is 70 meters long, how many kilometers does it travel per hour?
一位旅客乘火车以每秒15米的速度前进，他看见对面开来的火车只用2秒钟就从他身边驶过．如果知道迎面来的火车长70米，求它每小时行驶多少千米？
<result>72</result>