Two vehicles, A and B, depart from the mine and stockyard 63 kilometers apart at the same time, with speeds of 40 kilometers and 50 kilometers per hour respectively. How long did it take for the third encounter?
甲乙两辆汽车分别从相距63千米处的矿山与堆料场运料同时相向开出，时速分别为40千米和50千米，如果不计装卸时间，那么，两车往返运料自出发到第三次相遇共经过多少时间？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">40 + 50</gadget>
<output>90</output>

<gadget id="calculator">63 / 90</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">5 * (7/10)</gadget>
<output>7/2 = around 3.5</output>

<result>7/2 = around 3.5</result>