A and B practice running along the circular track in a clockwise direction. It is known that A takes 12 minutes to run a lap, and B takes 15 minutes to run a lap. So how many minutes after departure did A catch up with B?
甲乙两人按照顺时针的方向沿圆形跑道练习跑步，已知甲跑一圈要12分钟，乙跑一圈要15分，如果他们分别从圆形跑道的两端(半圈)同时出发，那么出发后多少分钟甲追上乙？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/12) - (1/15)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/2) / (1/60)</gadget>
<output>30</output>

<result>30</result>