How many kilograms of water are added to 20 kilograms of 15% salt water to obtain 5% salt water?
在20千克含盐15%的盐水中加多少千克水，可得到含盐为5%的盐水．
<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">20 * 3</gadget>
<output>60</output>

<gadget id="calculator">60 - 20</gadget>
<output>40</output>

<result>40</result>