Wang Hua practiced long-distance running on a section of the road. If he ran 0.5 kilometers per hour, the time would become the original (4/5). What was the original speed per hour?
王华在一段路上练习长跑，如果每小时多跑0.5千米，时间就变成原来的(4/5)，原来的速度是每小时多少．
<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(5/4) - 1</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">0.5 / (1/4)</gadget>
<output>2</output>

<result>2</result>