A barrel of oil is 100 kilograms, 25% is used, how many kilograms are left?
一桶油100千克，用去25%，还剩多少千克．
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">100 * (3/4)</gadget>
<output>75</output>

<result>75</result>