A grain stockpiles several tons. After 20% of the grain is shipped out, another 2,100 tons are shipped in. At this time, the grain stockpile is 40% more than before it was shipped out. How many tons of grain is there in this grain depot?
一个粮库存粮若干吨，运出20%后，又运进2100吨，这时粮库存粮比运出前多40%．这个粮库原有粮多少吨？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 + (2/5)</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(7/5) - (4/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">2_100 / (3/5)</gadget>
<output>3_500</output>

<result>3_500</result>