Xiao Wang wants to dilute 150 kg of pesticides with a 20% drug content into a 5% drug solution. How many kilograms of water need to be added?
小王要将150千克含药量20%的农药稀释成含药量5%的药水．需要加水多少千克？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/5) / (1/20)</gadget>
<output>4</output>

<gadget id="calculator">150 * 4</gadget>
<output>600</output>

<gadget id="calculator">600 - 150</gadget>
<output>450</output>

<result>450</result>