After the Wenchuan Earthquake, a rescue team of an engineering corps rushed to repair a tunnel, which had already been repaired (2/5), and half of the total length could be completed by repairing another 100 meters. How long is this tunnel in meters?
汶川地震后，某工程兵抢险队抢修一条隧道，已经修了(2/5)，再修100米，就可以完成全长的一半．这条隧道全长多少米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">100 / (1/10)</gadget>
<output>1_000</output>

<result>1_000</result>