The existing concentration of 20% sugar water is 350 grams, to turn it into 30% concentration of sugar water, how many grams of sugar should be added?
现有浓度为20%的糖水350克，要把它变成浓度为30%的糖水，需加糖多少克？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(4/5) / (7/10)</gadget>
<output>8/7 = around 1.142857</output>

<gadget id="calculator">350 * (8/7)</gadget>
<output>400</output>

<gadget id="calculator">400 - 350</gadget>
<output>50</output>

<result>50</result>