The construction site needs a batch of cement, all (2/5) is transported from the warehouse for the first time, the remaining (1/3) is transported for the second time, and the remaining (after the first two transports) is transported for the third time ( 3/4), at this time there were still 15 tons left to be transported. How many tons are there in total for this batch of cement?
建筑工地需要一批水泥，从仓库第一次运走全部的(2/5)，第二次运走余下的(1/3)，第三次运走(前两次运后)余下的(3/4)，这时还剩下15吨没运走．这批水泥原共有多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(3/5) * (1/3)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (2/5) - (1/5)</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/5) * (1/4)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">15 / (1/10)</gadget>
<output>150</output>

<result>150</result>