If 800 grams of 2.5% brine is used to make 4% brine, how many grams of water need to be evaporated?
用浓度为2.5%的盐水800克制成浓度为4%的盐水，需要蒸发掉多少克水．
<gadget id="calculator">2.5 / 100</gadget>
<output>0.025</output>

<gadget id="calculator">4 / 100</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">0.025 / (1/25)</gadget>
<output>0.625</output>

<gadget id="calculator">800 * 0.625</gadget>
<output>500</output>

<gadget id="calculator">800 - 500</gadget>
<output>300</output>

<result>300</result>