What is the difference between the reciprocal of (4/21) and the reciprocal of 21?
(4/21)的倒数与21的倒数的差是多少．
<gadget id="calculator">21 / 4</gadget>
<output>21/4 = around 5.25</output>

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

<gadget id="calculator">(21/4) - (1/21)</gadget>
<output>437/84 = around 5.202381</output>

<result>437/84 = around 5.202381</result>