The scatter plot below shows the number of pages by chapter for a prealgebra book.

(source: Pre-Algebra, Glencoe, 2003).

How many pages are in chapter 7?

Sample correct response: There are about 40 pages in chapter 7.

Which chapter has more pages, chapter 3 or chapter 4?

Sample correct response: Chapter 4 has more pages than chapter 3 because the data point for chapter 4 is higher on the graph than the data point for chapter 3. Also, chapter 4 has about 53 pages and chapter 3 has about 48 pages.

What is the mean number of pages in a chapter?

Sample correct response: The sum of the pages is 549. Divided by 10 (number of chapters) gives a mean of 54.9, which can be rounded to 55 pages.

Is there a relationship between the chapter number and the number of pages? Use the scatter plot to justify why your answer is correct. Use words, numbers, and/or symbols in your explanation.

Sample correct response: There number of pages in a chapter both increases and decreases as the chapter numbers increase, so there is no pattern or relationship. For example, chapter 5 has 65 pages, chapter 7 has about 40 (a decrease in number of pages) and chapter 8 jumps back up to 65 pages.

The scatter plot below shows the relationship between shoe lengths and arm spans of ten high school students.

What is the relationship of the shoe lengths and lengths of arm spans displayed in the scatter plot? Use the graph to justify why your answer is correct. Use words, numbers, and/or symbols in your justification.

Sample correct response:
As the shoe length increases, the arm span increases. For a shoe length of 25 cm, the arm span is 36 cm. For a shoe length of 27 cm, the arm span is 40 cm. It is generally true that the arm span increases as the shoe length increases.

Predict what the arm span will be for a student who has a shoe length of 30 cm? Explain how you found your answer. Use words, numbers, and/or symbols in your explanation.

Sample correct response:
I predict the arm span will be 58 cm. I saw that the relationship between the shoe length and arm span was positive by looking at the graph. In general, as the shoe length increased the arm span increased. To predict the arm span for a student with a shoe length of 30 cm, I connect the point where the shoe length was 29 cm to the point where the shoe length was 31 cm. I found the arm span for that point and it was close to 58 cm.