The average speed of the car is 65.71 mph.
The given parameters;
initial speed of the car, u = 50 mph
time of motion, t = 3 hours
final speed of the motion, v = 70 mph
time of motion, t = 11 hours
The average speed of the car is calculated as follows;
Average speed = total distance divided by the total time of motion.
The total distance = (50 x 3) + (70 x 11) = 920 miles
The total time of motion, = (3 + 11) = 14 hours.
The average speed of the car is;

Thus, the average speed of the car is 65.71 mph.
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