Here is a problem similar to the one in the last post, but with foibles of its own.
The speed of an airplane in miles per hour is given at half-hour intervals in the table below. Approximately how far does the airplane travel in the three hours given in the table? How far is it from the airport?
|Elapsed time (hours)||0||0.5||1||1.5||2||2.5||3|
|Speed (miles per hour)||375||390||400||390||385||350||345|
In addition to just finding the estimates, compare this situation with the Pump Problem from the last post. Some points to consider
- Answers between 1130 and 1145 miles are reasonable, if students proceed as they did with the Pump Problem. However, we cannot be sure since we do not know the speeds between the values recorded. In the Pump Problem we were told the pump was slowing down, so we could be sure the actual amount was between the values computed.
- Based on the information in the table what is the low and high estimates of the total distance? What assumptions do you make for these estimates. (Low = 1117.5 miles, high = 1157.5 miles assuming the plane flew at the slowest (fastest) speed in the table for the entirety of each 1/2-hour interval.)
- We also do not know where the plane started or which directions (plural) it was flying. So we have no way to tell how far it was from the airport (although we hope it gets to some airport eventually).
- What are the units? If we graph this as we did in the Pump Problem the various rectangles have dimensions of (miles/hour) by hours, so the “area” is miles (a linear unit).
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