1. Week 3! Warm-Up… Quickwrite…
Approximately how many books did you read in 2017? Approximately how many books do you think you will read in 2018? Why?
“In 2017 I read approximately ___ books, but in 2018 I think I will read ___ books because _________________________________________________________.”

2. Compare and Explain… your Warm-Up starting with Student #3 (1 min)
2,730

3. Round Robin…
starting with the student who has the biggest notebook at your table (1 min)
Approximately how many books did you read in 2017? Approximately how many books do you think you will read in 2018? Why?
“In 2017 I read approximately ___ books, but in 2018 I think I will read ___ books because _________________________________________________________.”

4. Practice
9. 24
10. 24
11. 36
12. a) 36
b) 9
c) 0.25
13. 20
15. 5,040
,880

5. Combinations

6. What about different groupings?
In each of our previous counting formulas, we have taken the order of the objects or people into account
However, suppose that in your English class you are given a list of 10 books and you are to select 4 to read during the semester
The order in which you read the books is not important. We are interested in the different groupings or combinations of 4 books from among the 10 on the list
The next formula tells us how to compute the number of different combinations

7. Ex: You are assigned to read any 4 books from a list of 10 books
Ex: You are assigned to read any 4 books from a list of 10 books. How many different groups of 4 are available from the list of 10?
In this case, we are interested in combinations, rather than permutations, of 10 books taken 4 at a time
Using n = 10 and r = 4, we have