A barrel of oil weighs 40 kilograms, 3/8 of the barrel of oil was used in the first week, and the remaining 20% was used in the second week. How many kilograms of oil are left in the barrel at this time?
一桶油重40千克，第一周用去了这桶油的(3/8)，第二周用去了剩下的20%．这时桶里的油还剩下多少千克？
<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">40 * (3/8)</gadget>
<output>15</output>

<gadget id="calculator">40 - 15</gadget>
<output>25</output>

<gadget id="calculator">20 / 100</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">25 * (4/5)</gadget>
<output>20</output>

<result>20</result>