The cafeteria bought a batch of rice, ate all of it (3/10) on the first day, and the rest (2/5) on the second day. At this time, there were 210 kilograms left. How many kilograms of this batch of rice were there in total?
食堂买来一批大米，第一天吃了全部的(3/10)，第二天吃了剩下的(2/5)，这时还剩下210千克，这批大米一共有多少千克．
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

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

<gadget id="calculator">(7/10) * (2/5)</gadget>
<output>7/25 = around 0.28</output>

<gadget id="calculator">1 - (3/10) - (7/25)</gadget>
<output>21/50 = around 0.42</output>

<gadget id="calculator">210 / (21/50)</gadget>
<output>500</output>

<result>500</result>