((1/11)+(1/21)+(1/31))((1/21)+(1/31)+(1/41))_((1/11)+(1/21 )+(1/31)+(1/41))((1/21)+(1/31))=how much.
((1/11)+(1/21)+(1/31))((1/21)+(1/31)+(1/41))_((1/11)+(1/21)+(1/31)+(1/41))((1/21)+(1/31))=多少．
<gadget id="calculator">1 / 11</gadget>
<output>1/11 = around 0.090909</output>

<gadget id="calculator">1 / 21</gadget>
<output>1/21 = around 0.047619</output>

<gadget id="calculator">1 / 31</gadget>
<output>1/31 = around 0.032258</output>

<gadget id="calculator">(1/11) + (1/21) + (1/31)</gadget>
<output>1_223/7_161 = around 0.170786</output>

<gadget id="calculator">1 / 41</gadget>
<output>1/41 = around 0.02439</output>

<gadget id="calculator">(1_223/7_161) * (1/41)</gadget>
<output>1_223/293_601 = around 0.004166</output>

<gadget id="calculator">(1/21) + (1/31)</gadget>
<output>52/651 = around 0.079877</output>

<gadget id="calculator">(52/651) * (1/41)</gadget>
<output>52/26_691 = around 0.001948</output>

<gadget id="calculator">(1_223/293_601) - (52/26_691)</gadget>
<output>1/451 = around 0.002217</output>

<result>1/451 = around 0.002217</result>