The cafeteria bought 100 kilograms of rice and ate (1/5), how many kilograms are left.
食堂买来100千克大米，吃了(1/5)，还剩下的千克数是多少千克．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

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

<result>80</result>