To determine the fastest average speed over the given intervals, we can calculate the average speed for each segment using the formula: speed = (distance at the end of interval - distance at the start of interval) / (time at the end of interval - time at the start of interval).
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Interval [0, 4]: Speed = (248 - 0) / (4 - 0) = 248 / 4 = 62 mph
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Interval [4, 7]: Speed = (449 - 248) / (7 - 4) = 201 / 3 = 67 mph
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Interval [7, 9]: Speed = (565 - 449) / (9 - 7) = 116 / 2 = 58 mph
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Interval [9, 12]: Speed = (757 - 565) / (12 - 9) = 192 / 3 = 64 mph
The average speed was fastest in the interval [4, 7] at 67 mph.