What is the sum of all the simplest proper fractions whose denominator is 12?
分母是12的所有最简真分数的和是多少．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">11 / 12</gadget>
<output>11/12 = around 0.916667</output>

<gadget id="calculator">(1/12) + (5/12) + (7/12) + (11/12)</gadget>
<output>2</output>

<result>2</result>