For a pile of sand, (1/4) of the total amount is transported away for the first time, 40 tons more than the first time for the second time, and 40% of the total amount for the third time, which is just finished. How many tons is this pile of sand?
一堆沙子，第一次运走总数的(1/4)，第二次比第一次多运走40吨，第三次运走总数的40%，正好运完．这堆沙子一共有多少吨？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/4) + (1/4) + (2/5)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">40 / (1/10)</gadget>
<output>400</output>

<result>400</result>