20*30 = <<20*30=600>>600 minutes have passed.

600/60 = <<600/60=10>>10 hours have passed.

# Answer

10
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
There is a road stretching 3 miles from the base camp to the chain challenge. Every 20 minutes, a car comes down the road from the base camp towards the chain challenge. How many hours have passed once 30 cars have come down the road?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
10
There is a road stretching 3 miles from the base camp to the chain challenge. Every 20 minutes, a car comes down the road from the base camp towards the chain challenge. How many hours have passed once 30 cars have come down the road?
train