supermarket buys a batch of rice, sells (2/5) tons on the first day, and sells the rest (2/5) on the second day, and the remaining rice is exactly half of this batch of rice. How many tons was this batch of rice originally?
某超市购进一批大米，第一天售出(2/5)吨，第二天售出余下的(2/5)，剩下的大米恰好是这批大米的一半．这批大米原来有多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * (2/5)</gadget>
<output>4/25 = around 0.16</output>

<gadget id="calculator">(2/5) - (4/25)</gadget>
<output>6/25 = around 0.24</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(6/25) / (1/10)</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>