How many grams of water should be evaporated when 400 grams of 5% brine is increased to 8% brine?
把400克浓度是5%的盐水，提高到浓度为8%的盐水应该蒸发多少克水．
<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">400 * (1/20)</gadget>
<output>20</output>

<gadget id="calculator">8 / 100</gadget>
<output>2/25 = around 0.08</output>

<gadget id="calculator">20 / (2/25)</gadget>
<output>250</output>

<gadget id="calculator">400 - 250</gadget>
<output>150</output>

<result>150</result>