Put 20 grams of salt into 100 grams of water, and after standing for three days, the evaporated salt water is only 100 grams. At this time, the concentration of salt water has increased by how many percent?
把20克盐放入100克水中，放置三天后蒸发后的盐水只有100克，这时盐水的浓度比原来提高了百分之几？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">100 + 20</gadget>
<output>120</output>

<gadget id="calculator">20 / 120</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/5) - (1/6)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/30) / (1/6)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>