Problem Statement:
Overnight shipment from Dallas, TX to Ithaca, NY:
Leg |
Departure |
Arrival |
Distance (miles) |
Transit Time (hr) |
Average Speed (mph) |
|---|---|---|---|---|---|
Dallas, TX to Memphis, TN |
9:15 p.m. |
12:25 a.m. |
426 |
||
Memphis, TN to Syracuse, NY |
3:44 a.m. |
7:06 a.m. |
926 |
||
Syracuse, NY to Ithaca, NY |
9:03 a.m. |
11:28 a.m. |
50.3 |
Fill in the missing columns in the above table. Which legs of the trip do you think were done by an airplane and which by a truck?
Solution:
Transit time = arrival time - departure time
Average speed = (distance)/(transit time)
Using these formulas to fill in the table we obtain:
Leg |
Departure |
Arrival |
Distance (miles) |
Time (hr) |
Average Speed (mph) |
|---|---|---|---|---|---|
Dallas, TX to Memphis, TN |
9:15 p.m. |
12:25 a.m. |
426 |
3.17 |
134 |
Memphis, TN to Syracuse, NY |
3:44 a.m. |
7:06 a.m. |
926 |
3.37 |
275 |
Syracuse, NY to Ithaca, NY |
9:03 a.m. |
11:28 a.m. |
50.3 |
2.42 |
20.8 |
Note: It is easier to compute the transit time if minutes are first converted to fractions of an hour. For example, 9:15 = 9 + 15/60 = 9.25 and 12:25 = 12 + 25/60 = 12.417 so the transit time for the first leg is 12.417 - 9.25 = 3.17 hr.
Based on the distance and average speed, the first two legs were probably done by airplane while the last leg was done by a truck. Note that the average speed includes time spent on the ground for the legs done by an airplane, so the average speed is lower than the actual flight speed for the aircraft. Most likely these legs were flown by turbofan-powered jet aircraft.