There is 5kg of salt water with a concentration of 10%, and now its concentration is increased to 20%, do you need to add salt or water? How many kilograms do I need to add?
有浓度为10%的盐水5kg，现在把它的浓度提高到20%，需要加盐还是加水？需要加多少千克呢？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(9/10) / (4/5)</gadget>
<output>9/8 = around 1.125</output>

<gadget id="calculator">5 * (9/8)</gadget>
<output>45/8 = around 5.625</output>

<gadget id="calculator">(45/8) - 5</gadget>
<output>5/8 = around 0.625</output>

<result>5/8 = around 0.625</result>