rectangular stadium is 250 meters wide. If a person walks around the stadium at a speed of 4 kilometers per hour, it takes 0.5 hours. How many hectares does the stadium occupy?
一个长方形体育场，宽是250米，如果一个人以每小时4千米的速度绕体育场走一圈，要用0.5小时，这个体育场占地多少公顷？
<gadget id="calculator">4 * 0.5</gadget>
<output>2</output>

<gadget id="calculator">1_000 / 2</gadget>
<output>500</output>

<gadget id="calculator">2 * 500</gadget>
<output>1_000</output>

<gadget id="calculator">1_000 - 250</gadget>
<output>750</output>

<gadget id="calculator">250 / 10_000</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">750 * (1/40)</gadget>
<output>75/4 = around 18.75</output>

<result>75/4 = around 18.75</result>