There is a batch of cement, 30% of the total amount was used for the first time, 1/4 of the total amount was used for the second time, and 2.7 tons remained in the last one. How many tons of cement was used for the second time?
有一批水泥，第一次用去总数的30%，第二次用去总数的(1/4)，最后的还剩下2.7吨．第二次用去水泥多少吨？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (3/10) - (1/4)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">2.7 / (9/20)</gadget>
<output>6</output>

<gadget id="calculator">6 * (1/4)</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>