A, B, and C start from A at the same time, and A, B, and C go around the lake counterclockwise along the time. A and C meet each other in 30 minutes, and B and C meet after another 5 minutes. A's speed is 5.4 km/h and B's is 4.2 km/h. Find the distance around the lake?
甲乙丙三人同时从A出发，甲乙顺时间丙逆时针绕湖而行．甲丙30分钟相遇，又过了5分钟乙丙相遇．甲的速度为5.4千米每小时，乙为4.2千米每小时．求绕湖一周的路程？
<gadget id="calculator">90 - 70</gadget>
<output>20</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">30 + 5</gadget>
<output>35</output>

<gadget id="calculator">1 / 35</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">(1/30) - (1/35)</gadget>
<output>1/210 = around 0.004762</output>

<gadget id="calculator">20 / (1/210)</gadget>
<output>4_200</output>

<result>4_200</result>