This is a very simple mathematical analysis topic. From the stem, we can know that Dad paid 16 yuan. It is known that the parking lot charges five yuan for one hour, and 3.5 yuan for more than half an hour, and seven yuan for more than one hour.

You can subtract 5.5 from 16 to calculate the amount of money exceeding 1 hour as 10.5 yuan, and then divide 10.5 by 7 to calculate 1.5 hours, that is, more than 1.5 hours, initially.

Money spent exceeding 1 hour: 16-5.5= 10.5 (yuan)

Charge per hour for exceeding 1 hour: 3.5÷0.5=7 (Yuan)

Time exceeding 1 hour:10.5÷ 7 =10.5 (hour)

* * * Parking time: 1+ 1.5=2.5 (hours)

So you can answer: Dad stopped for 2.5 hours.