Increase the concentration of 100 grams of sugar water containing 10% sugar to 20%, how many grams of water should be evaporated
把含糖10%的糖水100克的浓度提高到20%，应蒸发水多少克
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

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

<gadget id="calculator">(1/10) / (1/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">100 * (1/2)</gadget>
<output>50</output>

<gadget id="calculator">100 - 50</gadget>
<output>50</output>

<result>50</result>