For a pile of sand, (2/5) of the total tonnage is transported away for the first time, and the ratio of the second transported away is 3:4, and 15 tons are transported away for the third time, which happens to be all transported away. How many tons did this pile of sand originally weigh?
一堆砂子，第一次运走总吨数的(2/5)，与第二次运走的比是3：4，第三次运走15吨，正好全部运完．这堆砂子原来重多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">(2/5) / (3/4)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">1 - (2/5) - (8/15)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">15 / (1/15)</gadget>
<output>225</output>

<result>225</result>