Bus No. 7 departs every 20 minutes, and No. 8 bus departs every 15 minutes. They both depart the first shift at the same time. How many minutes must pass before the second departure at the same time?
7路车每20分钟发车一次，8路车每15分钟一次，它们同时发第一班，至少要经过多少分钟后才能第二次同时发车？
<gadget id="calculator">5 * 2 * 2 * 3</gadget>
<output>60</output>

<result>60</result>