If 415*A=713*B=1, then how much is AB=.
如果415*A=713*B=1，那么A-B=多少．
<gadget id="calculator">1 / 415</gadget>
<output>1/415 = around 0.00241</output>

<gadget id="calculator">1 / 713</gadget>
<output>1/713 = around 0.001403</output>

<gadget id="calculator">(1/415) - (1/713)</gadget>
<output>298/295_895 = around 0.001007</output>

<result>298/295_895 = around 0.001007</result>