The distance between A and B is 315 kilometers. A car and a motorcycle are traveling towards each other at the same time. The car travels 60 km per hour, and the distance between the two cars is 15 km after 3 hours. How many kilometers does the motorcycle travel per hour?
甲、乙两城相距315千米，一辆汽车和一辆摩托车同时相向而行．汽车每小时行驶60千米，3小时后两车相距15千米．摩托车每小时行驶多少千米？
<gadget id="calculator">315 - 15</gadget>
<output>300</output>

<gadget id="calculator">300 / 3</gadget>
<output>100</output>

<gadget id="calculator">100 - 60</gadget>
<output>40</output>

<result>40</result>