(1/5) of a barrel of oil is 20kg, how much is (4/5) of this barrel of oil in kg?
一桶油的(1/5)是20kg，这桶油的(4/5)是多少kg．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 / (1/5)</gadget>
<output>100</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">100 * (4/5)</gadget>
<output>80</output>

<result>80</result>