Question 852399
If it makes half a mile in 3 seconds, then it makes a whole mile in 6 seconds (impossible for a car).  
1 mile in 60 seconds = 1 mile per minute = 60 mph (60 minutes in an hour)
So 1 mile in 6 seconds would be ten times that, or 600 mph.
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Don't you love made-up questions that have no bearing on real life? :-D