SOLUTION: Junior drove his rig on Interstate 10 prom San Antonio to El Paso. At the halfway point he noticed that he had been averaging 80 MPH, while his company requires his average speed

Question 122329: Junior drove his rig on Interstate 10 prom San Antonio to El Paso. At the halfway point he noticed that he had been averaging 80 MPH, while his company requires his average speed to be 60 mph. What must his spped for the last half of the trip be so that he will average 60 mph for the entire trip?
Answer by checkley71(8403) (Show Source): You can put this solution on YOUR website!
.5/80+.5/x=1/60
(.5x+.5*80)/80x=1/60 now cross multiply.
80x=60(.5x+40)
80x=30x+2400
80x-30x=2400
50x=2400
x=2400/50
x=48 mph must be the speed for the last half of the trip.
proof
.5/80+.5/48=1/60
(.5*48+.5*80)/80*48=1/60
(24+40)/3840=1/60
64/3840=1/60
1/60=1/60
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