A potion for spraying fruit trees, the mass ratio of pesticide to water is 1:150. There are 3 kilograms of pesticides, how many kilograms of water need to be added to make pesticides with a mass ratio of pesticides and water of 1:200?
一种喷洒果树的药水，农药和水的质量比是1：150．现有3千克农药，需要加多少千克的水才能配成农药和水的质量比为1：200的农药？
<gadget id="calculator">200 + 1</gadget>
<output>201</output>

<gadget id="calculator">1 / 201</gadget>
<output>1/201 = around 0.004975</output>

<gadget id="calculator">3 / (1/201)</gadget>
<output>603</output>

<gadget id="calculator">150 + 1</gadget>
<output>151</output>

<gadget id="calculator">1 / 151</gadget>
<output>1/151 = around 0.006623</output>

<gadget id="calculator">3 / (1/151)</gadget>
<output>453</output>

<gadget id="calculator">603 - 453</gadget>
<output>150</output>

<result>150</result>