There is a cup of salt water weighing 300 grams, with a salt content of 20%, how many grams of water do you need to add to reduce the salt content to 10%?
有一杯重300克的盐水，含盐率为20%，要使含盐率下降为10%，需要加水多少克？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

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

<gadget id="calculator">300 * 2</gadget>
<output>600</output>

<gadget id="calculator">600 - 300</gadget>
<output>300</output>

<result>300</result>