Little Ding Ding ran 5 laps on a 400-meter circular track. How many kilometers did he run?
小丁丁在一圈是400米的环形跑道上跑了5圈，他跑了多少千米．
<gadget id="calculator">5 / 1_000</gadget>
<output>1/200 = around 0.005</output>

<gadget id="calculator">400 * (1/200)</gadget>
<output>2</output>

<result>2</result>