A, B, and C start from the same place by the lake and walk around the lake at the same time. A and B are going in the same direction, with speeds of 5.4 kilometers and 4.2 kilometers per hour, respectively. Meet once, and meet B in another 5 minutes. How many miles is the journey around the lake?
甲、乙、丙三人同时从湖边同一地点出发绕湖行走，甲、乙同向，速度分别为每小时5.4千米和4.2千米，丙与他们反向，30分钟后丙与甲第一次相遇，再过5分钟与乙相遇．则绕湖一周的行程是多少千米．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">5.4 * (1/2)</gadget>
<output>2.7</output>

<gadget id="calculator">4.2 * (1/2)</gadget>
<output>2.1</output>

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

<gadget id="calculator">4.2 * (1/12)</gadget>
<output>0.35</output>

<gadget id="calculator">2.7 - 2.1 - 0.35</gadget>
<output>0.25</output>

<gadget id="calculator">(1/12) - (1/2)</gadget>
<output>-5/12 = around -0.416667</output>

<gadget id="calculator">(1/2) + (-5/12)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">0.25 / (1/12)</gadget>
<output>3</output>

<gadget id="calculator">5.4 + 3</gadget>
<output>8.4</output>

<gadget id="calculator">8.4 * (1/2)</gadget>
<output>4.2</output>

<result>4.2</result>