To transport a batch of cement to the construction site, team A alone takes 10 days to transport it, and team B alone takes 8 days to transport it. After 3 days of joint transportation by the two teams, there are still 390 tons left undelivered. How many tons of cement are there in total?
将一批水泥运往建筑工地，甲队单独运要10天运完，乙队单独运要8天运完．两队合运3天后还剩下390吨没有运，这水泥共多少吨？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/10) + (1/8)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">(9/40) * 3</gadget>
<output>27/40 = around 0.675</output>

<gadget id="calculator">1 - (27/40)</gadget>
<output>13/40 = around 0.325</output>

<gadget id="calculator">390 / (13/40)</gadget>
<output>1_200</output>

<result>1_200</result>