200 grams of brine containing 16% salt, after evaporating part of the water, how much water needs to be evaporated to make the concentration of brine reach 20%?
含盐16%的盐水200克，蒸发部分水后，使盐水的浓度达到20%，需要蒸发多少水？
<gadget id="calculator">16 / 100</gadget>
<output>4/25 = around 0.16</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(4/25) / (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">200 * (4/5)</gadget>
<output>160</output>

<gadget id="calculator">200 - 160</gadget>
<output>40</output>

<result>40</result>