There are 200 grams of salt water with a salt content of 10%. Now it needs to be diluted with water to obtain a salt water with a salt content of 5%. How many grams of water should be added?
有200克含盐率是10%的盐水，现在需要加水稀释成含盐率是5%的盐水，需要加水多少克？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/10) / (1/20)</gadget>
<output>2</output>

<gadget id="calculator">200 * 2</gadget>
<output>400</output>

<gadget id="calculator">400 - 200</gadget>
<output>200</output>

<result>200</result>