A shipment of coal was originally scheduled to be finished within 7 days. 30% of the batch of coal was transported in the first three days, and 6,400 tons more coal was transported at this time than that which has been transported. How many tons will be transported on average every day in the future.
运送一批煤，原定7天运完．前三天运了这批煤的30%，这时没运的比已经运的多6400吨，以后平均每天要运多少吨．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10) - (3/10)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">6_400 / (2/5)</gadget>
<output>16_000</output>

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

<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">(7/10) / 4</gadget>
<output>7/40 = around 0.175</output>

<gadget id="calculator">16_000 * (7/40)</gadget>
<output>2_800</output>

<result>2_800</result>