Among (3/5), (4/7) and (5/9), what is the number closest to 0.5?
在(3/5)、(4/7)和(5/9)中，最接近0.5的数是多少．
<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<result>5/9 = around 0.555556</result>