There is a pile of sand, 35% of it is used for the first time, the remaining 20% is used for the second time, and 75% of the remaining 75% of the second time is used for the third time, leaving 15.6 cubic meters. How many cubic meters is this pile of sand originally? rice?
有一堆沙子，第一次用去35%，第二次用去余下的20%，第三次用去第二次剩下的75%，还剩下15.6立方米，这堆沙子原来有多少立方米？
<gadget id="calculator">35 / 100</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">1 - (7/20)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(13/20) * (1/5)</gadget>
<output>13/100 = around 0.13</output>

<gadget id="calculator">(13/20) - (13/100)</gadget>
<output>13/25 = around 0.52</output>

<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(13/25) * (3/4)</gadget>
<output>39/100 = around 0.39</output>

<gadget id="calculator">(13/25) - (39/100)</gadget>
<output>13/100 = around 0.13</output>

<gadget id="calculator">15.6 / (13/100)</gadget>
<output>120</output>

<result>120</result>