There is a tree every 50 meters on the side of the road. Jingjing counts from the first tree on the train to the 55th tree. After exactly 3 minutes, what is the speed of the train in kilometers per hour?
路旁每隔50米有一棵树，晶晶在火车上从第一棵树数起，数到第55棵为止，恰好过了3分钟，火车每小时的速度是多少千米．
<gadget id="calculator">55 - 1</gadget>
<output>54</output>

<gadget id="calculator">3 / 60</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">50 / (1/20) / 1_000</gadget>
<output>1</output>

<gadget id="calculator">54 * 1</gadget>
<output>54</output>

<result>54</result>