For a barrel of oil, 30% of it is used on the first day, and 10 kilograms are used on the second day. If the barrel of oil (2/5) is used for two days, how many kilograms of oil are left after two days of use.
一桶油，第一天用去它的30%，第二天用去10千克，两天共用去这桶油的(2/5)，则用去两天后还剩多少千克油．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/5) - (3/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">10 / (1/10)</gadget>
<output>100</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">100 * (3/5)</gadget>
<output>60</output>

<result>60</result>