Define a new operation a◎b=((ab)/(a+b)); 2◎10◎10=how much.
定义新运算a◎b=((ab)/(a+b))；2◎10◎10=多少．
<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">(5/3) * 10</gadget>
<output>50/3 = around 16.666667</output>

<gadget id="calculator">(5/3) + 10</gadget>
<output>35/3 = around 11.666667</output>

<gadget id="calculator">(50/3) / (35/3)</gadget>
<output>10/7 = around 1.428571</output>

<result>10/7 = around 1.428571</result>