If the number A is 80% of the number B, and the number B is 50% of the number C, then the number A is the number C.
甲数是乙数的80%，乙数又是丙数的50%，则甲数是丙数的多少．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / (1/2)</gadget>
<output>2</output>

<gadget id="calculator">(4/5) / 2</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>