A parking lot charges 3 yuan for one parking, and after more than 1 hour, an extra 1.5 yuan will be charged for each additional half hour. When the driver, Uncle Wang, drove his car away from the parking lot, he paid a total of 13.5 yuan for parking. How many hours did his car park in the parking lot at most?
某停车场停车一次收费3元，超过1小时后，每多停半小时加收1.5元．司机王叔叔从停车场开走他的车时，一共交了13.5元停车费，他的车在该停车场最多停了多少小时？
<gadget id="calculator">13.5 - 3</gadget>
<output>10.5</output>

<gadget id="calculator">1.5 + 1.5</gadget>
<output>3</output>

<gadget id="calculator">10.5 / 3</gadget>
<output>3.5</output>

<gadget id="calculator">3.5 + 1</gadget>
<output>4.5</output>

<result>4.5</result>