A barrel of oil, 10 kilograms are used, the remaining is less than the used (4/5), how many kilograms are the remaining less than the used?
一桶油，用去10千克，剩下的比用去的少(4/5)，剩下的比用去的少多少千克？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">10 * (4/5)</gadget>
<output>8</output>

<result>8</result>