A liquid medicine, the mass ratio of powder to water is 1:500. If there are 200 grams of such powder, how many kilograms of water should be added?
一种药水，药粉与水的质量比是1：500．如果有200克这样的药粉，需加水多少千克？
<gadget id="calculator">1 / 500</gadget>
<output>1/500 = around 0.002</output>

<gadget id="calculator">200 / (1/500) / 1_000</gadget>
<output>100</output>

<result>100</result>