There are 28 kilograms left in a barrel of oil, and the remaining 25% is used. How many kilograms are used?
一桶油剩下的是28千克，用去的是剩下的25%，用去的是多少千克？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">28 * (1/4)</gadget>
<output>7</output>

<result>7</result>