Clever calculation: (1/5)-(1/10)-(1/20)-(1/40)-(1/80)-(1/160)-(1/320).
巧算：(1/5)-(1/10)-(1/20)-(1/40)-(1/80)-(1/160)-(1/320)．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">1 / 80</gadget>
<output>1/80 = around 0.0125</output>

<gadget id="calculator">1 / 160</gadget>
<output>1/160 = around 0.00625</output>

<gadget id="calculator">1 / 320</gadget>
<output>1/320 = around 0.003125</output>

<gadget id="calculator">(1/5) - (1/10) - (1/20) - (1/40) - (1/80) - (1/160) - (1/320)</gadget>
<output>1/320 = around 0.003125</output>

<result>1/320 = around 0.003125</result>