For a pile of 20 tons of sand, 1/4 of the total amount is used for the first time, and 40% of the total amount is used for the second time, how many tons are used for the second time?
一堆沙20吨，第一次用去总数的(1/4)，第二次用去总数的40%，第二次用去多少吨？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 * (2/5)</gadget>
<output>8</output>

<result>8</result>