The rice in the grain store accounts for (3/7) of the total grain, and after selling 600 kg of rice, the rice accounts for (1/3) of the total grain. How many kilograms of grain did this grain store have in total?
粮店中的大米占粮食总量的(3/7)，卖出600千克大米后，大米占粮食总量的(1/3)．这个粮店原来共有粮食多少千克．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">600 * (1/3)</gadget>
<output>200</output>

<gadget id="calculator">600 - 200</gadget>
<output>400</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(3/7) - (1/3)</gadget>
<output>2/21 = around 0.095238</output>

<gadget id="calculator">400 / (2/21)</gadget>
<output>4_200</output>

<result>4_200</result>