A glass of 500ml sugar water has a sugar content of 30%. After drinking half of it, add 250ml of water. What is the sugar content now?
一杯500ml糖水，含糖量为30%，喝掉一半后，再加250ml的水，现在含糖多少．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">500 / 2</gadget>
<output>250</output>

<gadget id="calculator">250 + 250</gadget>
<output>500</output>

<gadget id="calculator">(3/10) / 2 / 500</gadget>
<output>3/10_000 = around 0.0003</output>

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

<gadget id="calculator">500 * (3/10_000) * 1</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>