Divide 4 tons of coal into 9 parts on average, each part is 4 tons ((())/(())), how many tons is each part.
把4吨煤平均分成9份，每份是4吨的((())/(()))，每份是多少吨．
<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">1 / (1/9) / 1</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<result>4/9 = around 0.444444</result>