A bag of rice weighs 40 kg. After 20% is used, the remaining 20% is put in. How much does the bag of rice weigh?
一袋米重40千克，用了20%之后，又放入剩下的20%，这时这袋米重多少千克．
<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">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">40 * (4/5) * (6/5)</gadget>
<output>192/5 = around 38.4</output>

<result>192/5 = around 38.4</result>