Master Zhang drove a truck from the county seat to the provincial capital to deliver the goods. After arriving in the provincial capital, he immediately unloaded the goods and then returned along the original road. The car he drove traveled 64 kilometers per hour when going out, and 56 kilometers per hour when returning. It took 12 hours for a round trip (the time spent in unloading in the provincial capital was omitted). How many kilometers did Master Zhang travel back and forth between the provincial capital and the county seat?
张师傅驾驶一辆载重汽车从县城出发到省城送货，到达省城后马上卸货并随即沿原路返回．他驾驶的这辆汽车去时每小时行64千米，返回时每小时行56千米，往返一趟共用去12小时(在省城卸货所用时间略去不计)．张师傅在省城和县城之间往返一趟共行了多少千米？
<gadget id="calculator">7 + 8</gadget>
<output>15</output>

<gadget id="calculator">7 / 15</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">12 * (7/15)</gadget>
<output>28/5 = around 5.6</output>

<gadget id="calculator">64 * (28/5) * 2</gadget>
<output>3_584/5 = around 716.8</output>

<result>3_584/5 = around 716.8</result>