(3/(2*5))+(3/(5*8))+(3/(8*11))+…+(3/(1991*1994))+(3/(1994*1997) ) = how much.
(3/(2*5))+(3/(5*8))+(3/(8*11))+…+(3/(1991*1994))+(3/(1994*1997))=多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 1_997</gadget>
<output>1/1_997 = around 0.000501</output>

<gadget id="calculator">(1/2) - (1/1_997)</gadget>
<output>1_995/3_994 = around 0.499499</output>

<result>1_995/3_994 = around 0.499499</result>