A pile of sand, 40% of the pile of sand is transported for the first time, 50% of the sand is transported for the second time, and 45 tons more than the first time is transported for the second time. How many tons is this pile of sand?
一堆沙子，第一次运走这堆沙子的40%，第二次运走这堆沙子的50%，第二次比第一次多运45吨．这堆沙子共有多少吨？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

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

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

<gadget id="calculator">45 / (1/10)</gadget>
<output>450</output>

<result>450</result>