The fast and slow trains leave oppositely from two places 135 kilometers apart at the same time, and meet after 1 hour. If the speed of the fast car is twice that of the slow car, how many kilometers does the slow car travel per hour?
快、慢两车同时从相距135千米的两地相对开出，1小时后相遇．如果快车的速度为慢车的2倍，那么慢车每小时行了多少千米？
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">135 / 3</gadget>
<output>45</output>

<result>45</result>