There are three fractions, the numerators are all 1, and the denominators are the smallest prime number, the smallest composite number, and the smallest odd number. What is the sum of these three fractions?
有三个分数，分子都是1，分母分别是最小的质数、最小的合数、奇数中最小的合数，这三个分数的和是多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/2) + (1/4) + (1/9)</gadget>
<output>31/36 = around 0.861111</output>

<result>31/36 = around 0.861111</result>