A bottle of sugar water with a sugar content of 40%, pour out 40% and then fill up with water, what is the concentration of the sugar water at this time?
一瓶含糖率40%的糖水，倒出40%后，再加满水，这时糖水的浓度多少．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) / 1</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(2/5) * (3/5)</gadget>
<output>6/25 = around 0.24</output>

<result>6/25 = around 0.24</result>