A train from Shanghai to Hankou has already passed (3/5), and it is still 400 kilometers away from Hankou. How many kilometers is the railway from Shanghai to Hankou?
一列火车从上海开往汉口，已经行了(3/5)，离汉口还有400千米．上海到汉口的铁路长多少千米？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">400 / (2/5)</gadget>
<output>1_000</output>

<result>1_000</result>