There is a tree every 50 meters next to the railway. Qiangqiang counted from the first tree on the train to the 61st tree. After exactly 6 minutes, what is the speed of the train in kilometers per hour?
铁路旁每隔50米有一棵树，强强在火车上从第一棵树数起，数到第61棵为止，恰好过了6分钟，火车每小时的速度是多少千米．
<gadget id="calculator">61 - 1</gadget>
<output>60</output>

<gadget id="calculator">6 / 60</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">50 / (1/10) / 1_000</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">60 * (1/2)</gadget>
<output>30</output>

<result>30</result>