It takes 2 minutes for an express train to pass through an 800-meter-long tunnel at a speed of 500 meters per minute. How long is the body of the express train in meters?
一列特快列车以每分钟500米的速度通过长800米的隧道，用了2分钟，特别快车的车身长多少米．
<gadget id="calculator">500 * 2</gadget>
<output>1_000</output>

<gadget id="calculator">1_000 - 800</gadget>
<output>200</output>

<result>200</result>