The Beijing-Tianjin intercity railway will be put into operation on August 1, 2008. It is estimated that the one-way direct running time of high-speed trains between Beijing and Tianjin will be half an hour. During a test run, the travel time of the test train from Beijing to Tianjin took 6 minutes longer than the expected time, and the travel time from Tianjin to Beijing was the same as the expected time. If during the test run, the average speed of returning from Tianjin to Beijing is 40 kilometers per hour more than that of going to Tianjin, how many kilometers per hour is the average speed from Beijing to Tianjin during the test drive? (positive and negative ratio)
京津城际铁路将于2008年8月1日开通运营，预计高速列车在北京、天津间单程直达运行时间为半小时．某次试车时，试验列车由北京到天津的行驶时间比预计时间多用了6分钟，由天津返回北京的行驶时间与预计时间相同．如果这次试车时，由天津返回北京比去天津时平均每小时多行驶40千米，那么这次试车时由北京到天津的平均速度是每小时多少千米？(正反比例)
<gadget id="calculator">40 * 30</gadget>
<output>1_200</output>

<gadget id="calculator">6 - 30</gadget>
<output>-24</output>

<gadget id="calculator">30 + (-24)</gadget>
<output>6</output>

<gadget id="calculator">1_200 / 6</gadget>
<output>200</output>

<result>200</result>