The existing 2 kg of disinfectant containing 60% medicine needs to be mixed with water to make a liquid medicine containing 0.5% medicine for disinfection. How many kilograms of water should be added?
现有含药60%的消毒剂2千克，需要加清水配成含药0.5%的药水进行消毒，需加清水多少千克？
<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">0.5 / 100</gadget>
<output>0.005</output>

<gadget id="calculator">(3/5) / 0.005</gadget>
<output>120</output>

<gadget id="calculator">2 * 120</gadget>
<output>240</output>

<gadget id="calculator">240 - 2</gadget>
<output>238</output>

<result>238</result>