The existing salt water with a salt content of 20% is 300 grams. If the salt content is to be reduced to 10%, how many grams of water should be added?
现有含盐率为20%的盐水300克，如果要使含盐率降为10%，应加水多少克？
<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>