A potion for spraying fruit trees, the mass ratio of pesticide to water is 3:500. The existing water is 300 kg, how many kg of pesticides need to be added?
一种喷洒果树的药水，农药和水的质量比是3：500．现有水300千克，需要加农药多少千克？
<gadget id="calculator">3 / 500</gadget>
<output>3/500 = around 0.006</output>

<gadget id="calculator">(3/500) * 300</gadget>
<output>9/5 = around 1.8</output>

<result>9/5 = around 1.8</result>