John drives for 3 hours at a speed of 60 mph and then turns around because he realizes he forgot something very important at home.  He tries to get home in 4 hours but spends the first 2 hours in standstill traffic.  He spends the next half-hour driving at a speed of 30mph, before being able to drive the remaining time of the 4 hours going at 80 mph.  How far is he from home at the end of those 4 hours?
When he turned around he was 3*60=<<3*60=180>>180 miles from home
He was only able to drive 4-2=<<4-2=2>>2 hours in the first four hours
In half an hour he goes 30*.5=<<30*.5=15>>15 miles
He then drives another 2-.5=<<2-.5=1.5>>1.5 hours
In that time he goes 80*1.5=<<80*1.5=120>>120 miles
So he drove 120+15=<<120+15=135>>135 miles
So he is 180-135=<<180-135=45>>45 miles away from home
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