What is (2/21) of (3/7).
(3/7)的(2/21)是多少．
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">2 / 21</gadget>
<output>2/21 = around 0.095238</output>

<gadget id="calculator">(3/7) * (2/21)</gadget>
<output>2/49 = around 0.040816</output>

<result>2/49 = around 0.040816</result>