There are 200 kilograms of brine with a salt content of 15%, how many kilograms of water need to be added to reduce the salt content to 5%?
有含盐15%的盐水200千克，要使含盐率降为5%，需要加水多少千克？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

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

<gadget id="calculator">(3/20) / (1/20)</gadget>
<output>3</output>

<gadget id="calculator">200 * 3</gadget>
<output>600</output>

<gadget id="calculator">600 - 200</gadget>
<output>400</output>

<result>400</result>