A bucket full of 40kg of salt water containing 12.5% salt is first poured out (1/5), then filled up with water, then poured out half and then filled up with water, find the salt content of the bucket at this time.
满桶含盐12.5%的盐水40千克，先倒出(1/5)后，加满水，又倒出一半再加满水，求这时这桶盐水的含盐率．
<gadget id="calculator">12.5 / 100</gadget>
<output>0.125</output>

<gadget id="calculator">1 / 5</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">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) / 40</gadget>
<output>1/80 = around 0.0125</output>

<gadget id="calculator">40 * 0.125 * (4/5) * (1/80)</gadget>
<output>0.05</output>

<result>0.05</result>