If 80 grams of salt water with a concentration of 20% is added to 20 grams of water, what is the concentration of salt water at this time?
现有浓度为20%的盐水80克，加入20克水，这时盐水的浓度是多少？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">80 + 20</gadget>
<output>100</output>

<gadget id="calculator">(1/5) / 100</gadget>
<output>1/500 = around 0.002</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">80 * (1/500) * 1</gadget>
<output>4/25 = around 0.16</output>

<result>4/25 = around 0.16</result>