Fill a 500ml cup with milk. Drink half of it for the first time and top up with coffee; drink half of it for the second time and top up with coffee; drink half of it for the third time and top up with coffee. How many milliliters of pure milk is left at this time.
在容积为500毫升的杯子内装满牛奶．第一次喝去一半，加满咖啡；第二次再喝去一半，加满咖啡；第三次又喝去一半，再加满咖啡．这时还有多少毫升纯牛奶．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">500 * (1/2)</gadget>
<output>250</output>

<gadget id="calculator">500 * (1/2) * (1/2)</gadget>
<output>125</output>

<gadget id="calculator">500 * (1/2) * (1/2) * (1/2)</gadget>
<output>125/2 = around 62.5</output>

<gadget id="calculator">250 + 125 + (125/2)</gadget>
<output>875/2 = around 437.5</output>

<gadget id="calculator">500 - (875/2)</gadget>
<output>125/2 = around 62.5</output>

<result>125/2 = around 62.5</result>