David W. answered • 10/03/15
Tutor
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Experienced Prof
Robert,
Bill P. specified the math calculation; Britt K. provided a number; I'll simply comment.
If this is merely a contrived math problem, then the calculated travel time is based either on a constant rate (which, of course, is impossible since you must certainly start, stop, speed up and slow down during the trip -- for example, no manufactured automobile can travel continuously for 8 hours without refueling and most people need "pit stops") or an average rate (and that means as much travel above 78 miles/hour as there is below 78 miles/hour). Those clarifications are extremely important (for safety, legal, etc. reasons).
The difference between the plan and the actual performance (called the variance) is a major focus of project management -- costs overrun estimates, projects are late, scope creeps (and there is "gold plating"), people change jobs, etc. etc.
Look at it this way --> Absolutely no one would accept the risk to bid on a contract to drive you safely and legally from Santa Fe to Las Vegas in a fixed time of 8 hours at any price (but you might try flying).
