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Private: Learning Math: Measurement
What Does It Mean To Measure? Homework
Session 1, Homework
How Large Is It?
This table shows the height to the shoulder and the weight of several species of buffalo. Which is the largest (i.e., one that is both tall and heavy)? The guar is the tallest, and the water buffalo and the American bison are the heaviest, but how might we determine which is the largest?
| Name (Country/Continent) |
Height (cm) |
Weight (kg) |
| Water Buffalo (Asia) | 165 | 1,000 |
| African Buffalo | 135 | 560 |
| Yak (Tibet) | 200 | 550 |
| Guar (Asia) | 220 | 850 |
| American Bison (North America) | 180 | 1,000 |
| European Bison | 200 | 900 |
Problem H1
Maria decides to add the height and the weight as a measure of the total size. The animal with the greatest sum is the largest.
Which three animals, in order from largest to smallest, are the largest, according to Maria’s criterion?
Problem H2
Jacob decides to rank the animals from 1 to 6 for both height and weight. The smallest in each category is given a rank of 1, the largest a rank of 6. If two animals have the same height or weight, each receives the average of the ranks they would have received. He then adds the height and weight ranks. The largest sum indicates the largest animal.
Which three animals, in order from largest to smallest, are largest according to Jacob’s system?
Problem H3
Quentin decides to find the product of height and weight as a measure of the total size.
Which three animals, in order from largest to smallest, does Quentin think are the largest?
Problem H4
Is Quentin’s method a good measure of how large an animal is? Do you think it is better or worse than Jacob’s method?
Problem H5
Greg argues that the question would be easier to decide if one of the buffalo were 220 cm tall to the shoulder and weighed 1,000 kg. That animal would clearly be the largest, because it would be both the tallest and the heaviest.
a. Plot the height and weight of each buffalo as an ordered pair. You may want to print out the image (PDF) of the axes below to plot the points.
| Heights and Weights of Buffalo |
 |
b. How far from the point (220,1000) does each buffalo fall? Which point is the shortest distance away? Complete this table:
| Name (Country/Continent) |
Coordinates |
Distance from (220,1000) |
| Water Buffalo (Asia) | (165,1000) | |
| African Buffalo | (135,560) | |
| Yak (Tibet) | (200,550) | |
| Guar (Asia) | (220,850) | |
| American Bison (N. America) | (180,1000) | |
| European Bison | (200,900) |
Use the Pythagorean theorem to find distances between two points. Imagine a right triangle whose hypotenuse lies between the two points and whose legs are parallel to the x- and y-axes (the right angle between them). The shortest distance between the points will be the length of the hypotenuse. How can you use the coordinates of the two points to figure out the lengths of the legs you will need in order to calculate the length of the hypotenuse?
Problem H6
Which three species, in order from largest to smallest, are closest to the point (220,1000)?
Marcy alters Greg’s argument somewhat. She argues that the smallest animal would be (0,0), or no animal at all. Since largest is the opposite of smallest, the largest animal is the one farthest from (0,0).
Problem H7
Which three buffalo, in order from largest to smallest, are largest by Marcy’s rule? Complete the table below.
| Name (Country/Continent) |
Coordinates |
Distance from (0,0) |
| Water Buffalo (Asia) | (165,1000) | |
| African Buffalo | (135,560) | |
| Yak (Tibet) | (200,550) | |
| Guar (Asia) | (220,850) | |
| American Bison (N. America) | (180,1000) | |
| European Bison | (200,900) |
In all the criteria used so far, the students equate 1 cm in height to 1 kg in weight. It is not always reasonable to treat all units of measure as being equally important. For example, Maurice thinks that a 1 cm increase in height is more noticeable than a 1 kg increase in weight. In fact, he believes that a 1 cm change in height is twice as important as a 1 kg change in weight, so he uses the value of the expression 2(height) + weight as his measure. According to Maurice’s rule, the largest animal is the American bison, followed by the water buffalo and the European bison.
Problem H8
How would you have solved this problem? Can you think of an additional rule that can be used to determine which three animals are the largest?
Problem H9
Which species of buffalo would you say is the smallest? Why?
Solutions
Problem H1
According to Maria’s criterion, here are the values:
| Name (Country/Continent) |
Height (cm) + Weight (kg) |
| Water Buffalo (Asia) | 1,165 |
| African Buffalo | 695 |
| Yak (Tibet) | 750 |
| Guar (Asia) | 1,070 |
| American Bison (North America) | 1,180 |
| European Bison | 1,100 |
The three largest animals by this criterion are the American bison, the water buffalo, and the European bison.
Note that this method is somewhat problematic since the answers could change drastically if we change the units of measurement. For example, the results would look quite different if we measured weight in tons (1 metric ton = 1,000 kg) instead of in kilograms. Clearly, this can lead to potential errors.
Problem H2
Here are the ranks according to Jacob’s criterion:
| Name (Country/Continent) | Height Rank | Weight Rank | Total |
| Water Buffalo (Asia) | 2 | 5.5 (tie) | 7.5 |
| African Buffalo | 1 | 2 | 3 |
| Yak (Tibet) | 4.5 (tie) | 1 | 5.5 |
| Guar (Asia) | 6 | 3 | 9 |
| American Bison (North America) | 3 | 5.5 (tie) | 8.5 |
| European Bison | 4.5 (tie) | 4 | 8.5 |
The three largest animals by this criterion are the guar, the American bison, and the European bison.
Problem H3
Here are the products for each animal:
| Name (Country/Continent) |
Height (cm) • Weight (kg) |
| Water Buffalo (Asia) | 165,000 |
| African Buffalo | 75,600 |
| Yak (Tibet) | 110,000 |
| Guar (Asia) | 187,000 |
| American Bison (North America) | 180,000 |
| European Bison | 180,000 |
The three largest animals by Quentin’s criterion are the guar, the American bison, and the European bison.
Problem H4
These two methods result in the same ordering of the animals, but some may argue that Quentin’s method is more capricious than Jacob’s, since there is no natural meaning to multiplying height and weight.
Problem H5
-
- Using the Pythagorean theorem, we can derive a formula for the distance between two points A (x1,y1) and B (x2,y2) as
Next, we can calculate the distances. So for the Asian water buffalo 
Here is the completed table:
Name (Country/Continent) Coordinates
Distance from (220,1000)
Water Buffalo (Asia) (165,1000) 55 African Buffalo (135,560) 448.13 Yak (Tibet) (200,550) 450.44 Guar (Asia) (220,850) 150 American Bison (North America) (180,1000) 40 European Bison (200,900) 101.98
To learn more about the Pythagorean theorem and distance formula, go to Learning Math: Geometry, Session 6.
Problem H6
The three species closest to (220,1000) are the American bison, the water buffalo, and the European bison.
Problem H7
Here is the completed table:
| Name (Country/Continent) |
Coordinates |
Distance from (0,0) |
| Water Buffalo (Asia) | (165,1000) | 1,013.52 |
| African Buffalo | (135,560) | 576.04 |
| Yak (Tibet) | (200,550) | 585.23 |
| Guar (Asia) | (220,850) | 878.01 |
| American Bison (North America) | (180,1000) | 1,016.07 |
| European Bison | (200,900) | 921.95 |
According to Marcy’s criterion, the three largest animals are the American bison, the water buffalo, and the European bison.
Problem H8
Answers will vary. Another possible method is to use weight as the first determining factor and to use height only in case of a tie.
Problem H9
Answers will vary, but the most likely answer is the African buffalo, which is the shortest and nearly the lightest. It wins easily on Jacob’s criterion and is the smallest for many others.
