Using a tractor to plow the land, (1/2) hours plowed (11/9) hectares, which is exactly equivalent to (11/21) of this land. How many hectares is this land?
用拖拉机耕地，(1/2)小时耕了(11/9)公顷，正好相当于这块地的(11/21)．这块地有多少公顷？
<gadget id="calculator">11 / 9</gadget>
<output>11/9 = around 1.222222</output>

<gadget id="calculator">11 / 21</gadget>
<output>11/21 = around 0.52381</output>

<gadget id="calculator">(11/9) / (11/21)</gadget>
<output>7/3 = around 2.333333</output>

<result>7/3 = around 2.333333</result>