Calculation: ((1/2)+(1/3)+(1/4)+…(1/20))+((2/3)+(2/4)+(2/5)+…+ (2/20))+((3/4)+(3/5)+(3/6)+...+(3/20))+...+(19/20).
计算：((1/2)+(1/3)+(1/4)+…(1/20))+((2/3)+(2/4)+(2/5)+…+(2/20))+((3/4)+(3/5)+(3/6)+…+(3/20))+…+(19/20)．
<gadget id="calculator">21 / 4</gadget>
<output>21/4 = around 5.25</output>

<gadget id="calculator">20 * (21/4)</gadget>
<output>105</output>

<result>105</result>