First find the number of cars in Section G by multiplying the number of rows by the number of cars per row: 15 rows * 10 cars/row = <<15*10=150>>150 cars
Then do the same thing for Section H: 20 rows * 9 cars/row = <<20*9=180>>180 cars
Then add the two quantities of cars to find the total number of cars Nate walked past: 150 cars + 180 cars = <<150+180=330>>330 cars
Finally, divide the number of cars Nate passed by the numbers he passes each minute to find how long he spent searching: 330 cars / 11 cars/minute = <<330/11=30>>30 minutes
#### 30