Chester was going from Hualien to Lukang, Changhua to participate in the Hua Luogeng Gold Cup Math Competition. Before he drove out, his father looked at the odometer of the car. The results of the numbers read on the left are the same). After driving for 5 hours in a row to arrive at the destination, the odometer just happened to be another palindrome number. During the journey, Dad never drove at a speed exceeding 85 kilometers per hour. What is the maximum average speed of Dad’s driving in kilometers per hour? ．
切斯特要从花莲赴彰化鹿港参加华罗庚金杯数学竞赛，爸爸开车出门前看了一下车子的里程表，刚好是一个回文数69696公里(回文数：从左到右，或从右到左读到的数字结果都一样)．一连开了5个小时到达目的地，到达时里程表又刚好是另一个回文数，在路程中，爸爸开车的时速从未超过85公里，请问爸爸开车的平均速度最大值是每小时多少公里．
<gadget id="calculator">70_107 - 69_696</gadget>
<output>411</output>

<gadget id="calculator">411 / 5</gadget>
<output>411/5 = around 82.2</output>

<result>411/5 = around 82.2</result>