The medicine and water are prepared according to the ratio of 1:500, how much medicine powder should be added to 40 kg of water.
药和水按1：500的比例配制药水，40千克水中应加药粉多少．
<gadget id="calculator">1 / 500</gadget>
<output>1/500 = around 0.002</output>

<gadget id="calculator">(1/500) * 40</gadget>
<output>2/25 = around 0.08</output>

<result>2/25 = around 0.08</result>