Two people, A and B, start from A and B, which are 6 kilometers apart, and walk back and forth between A and B. A walks 6 kilometers per hour, and B walks 4 kilometers per hour. How long does it take after departure? The third time the two met head-to-head? How long did it take for A to catch up with B for the third time?
甲、乙两人分别从相距6千米的A、B两地出发，在A、B之间往返走，甲每小时走6千米，乙每小时走4千米，出发后多长时间，两人第三次迎面相遇？又过了多长时间，甲第三次追上乙？
<gadget id="calculator">30 + 20</gadget>
<output>50</output>

<gadget id="calculator">3 / 50</gadget>
<output>3/50 = around 0.06</output>

<gadget id="calculator">300 * 2 * (3/50)</gadget>
<output>36</output>

<result>36</result>