MATH 267: Introduction to Abstract Math

Fall 2026


Written Assignments (collected)

Written assignments ask for a small number of proofs written up carefully, in full sentences, the way you would want them to appear in a book. They are graded on the writing as well as on the mathematics: an argument that is correct but unreadable will not receive full credit. Each assignment will be posted here at least a week before it is due.

You may collaborate on these, but you must write your final solutions in your own words and list your collaborators at the top of the page. See the course policies for details.


Assignment Due Files
Written Assignment 1 (Chapters 2–4) Wednesday, September 9 Assignment (PDF)


Practice Problems (not collected)

A word about the two kinds of problems in the book. Gorkin and Daepp distinguish Exercises, which appear inside the body of each chapter and have complete solutions at the end of that chapter, from Problems, which appear at the end of the chapter and do not. Work the Exercises as you read - that is what they are for, and checking your answer immediately is the point. The practice problems listed below are all Problems.

These are not collected. Nobody will check whether you did them. They are also the single best predictor of how you will do on the quizzes and exams, which between them are 70% of your grade. Quiz problems will frequently be one of these problems, or a close relative of one.

How to use the list. Do not read a problem, decide you know how it would go, and move on. Write the proof out in full sentences. The gap between "I see why this is true" and "I can write an argument that convinces a skeptical reader" is exactly what this course is about, and it only becomes visible when you put a pen down on paper. If you get stuck for more than fifteen minutes or so on a problem, that is a good problem to bring to office hours.

A problem marked is one I particularly recommend; these tend to be the ones that either come up again later or catch a common misunderstanding.


Date Chapter Problems
Week 1
8/24 1. The How, When, and Why of Mathematics 1.2, 1.3, 1.4, 1.5, 1.6, 1.9 , 1.12
8/26 2. Logically Speaking 2.1, 2.2 , 2.3 , 2.5, 2.7, 2.8, 2.11, 2.17, 2.19, 2.20
Week 2
8/31 3. Contrapositive and Converse 3.2 , 3.3, 3.5, 3.6, 3.7, 3.9, 3.14, 3.15, 3.18
9/2 4. Set Notation and Quantifiers 4.1, 4.2, 4.4, 4.5 , 4.10, 4.11, 4.13, 4.14, 4.16, 4.18
Week 3
9/7No Class - Labor Day
9/9 5. Proof Techniques (direct proof, contrapositive) 5.2, 5.3, 5.7, 5.8 , 5.9 , 5.12, 5.14
Week 4
9/14 5. Proof Techniques (contradiction, cases, counterexamples) 5.10 , 5.11, 5.13, 5.15, 5.17, 5.21, 5.25 , 5.28
9/16 6. Sets 6.1, 6.2 , 6.3, 6.5, 6.11, 6.12, 6.13, 6.19, 6.20, 6.22
Week 5
9/21 7. Operations on Sets 7.2, 7.3, 7.4, 7.6 , 7.9, 7.15, 7.17
9/23 8. More on Operations on Sets (indexed families) 8.1, 8.2, 8.3, 8.4, 8.7, 8.12
Week 6
9/28 9. The Power Set and the Cartesian Product 9.1, 9.2, 9.3, 9.4, 9.5 , 9.8 , 9.11, 9.13, 9.15, 9.19
9/30 10. Relations 10.1, 10.2, 10.5, 10.6, 10.7, 10.8, 10.10 , 10.11 , 10.12
Week 7
10/5 Review (Chapters 1-10, ~50 min), then 11. Partitions (begin) Review: rework any problem above that you could not finish the first time, without looking at your earlier attempt.
11.1, 11.2, 11.3 , 11.5, 11.11, 11.12, 11.13, 11.21
10/7 Midterm Exam 1 (Chapters 1-10, 75 minutes), then 11. Partitions (continued)
Week 8
10/12 12. Order in the Reals 12.1 , 12.2, 12.3, 12.5, 12.6, 12.8 , 12.9, 12.10, 12.17, 12.18
10/14 Catch-up day - no new problems
Week 9
10/19 14. Functions, Domain, and Range 14.1 , 14.2, 14.3, 14.5, 14.11, 14.14, 14.15, 14.16, 14.20
10/21 15-16. Injections, Surjections, Inverses 15.1, 15.2, 15.3, 15.5 , 15.7, 15.10, 15.13
16.1, 16.2, 16.5, 16.7, 16.9 , 16.12
Week 10
10/26 17. Images and Inverse Images 17.1, 17.2, 17.3, 17.4, 17.9, 17.10 , 17.13, 17.18 , 17.19
10/28 Catch-up day - no new problems
Week 11
11/2 18. Mathematical Induction 18.1, 18.2, 18.3, 18.4, 18.5 , 18.8, 18.9
11/4 18. Complete Induction, Recursion, Well Ordering 18.6, 18.7, 18.15 , 18.16, 18.20, 18.21 , 18.24, 18.26
Week 12
11/9 19. Sequences 19.1, 19.2, 19.3, 19.6 , 19.7, 19.8, 19.9, 19.18
11/11 20. Convergence of Sequences of Real Numbers 20.1, 20.2, 20.3, 20.4 , 20.5 , 20.8, 20.9
Week 13
11/16 20. Cauchy Sequences and Completeness 20.11 , 20.12, 20.17, 20.21, 20.22, 20.23
11/18 Midterm Exam 2 (Chapters 12, 14-20)
Week 14
11/23 21. Equivalent Sets 21.1, 21.2, 21.4 , 21.6, 21.7, 21.15, 21.20, 21.21
11/25No Class - Thanksgiving Holiday
Week 15
11/30 22-24. Finite Sets, Countability, Cantor-Schröder-Bernstein 22.2, 22.3, 22.8 , 22.9, 22.15, 22.21
23.1, 23.2, 23.3, 23.4 , 23.6
24.2, 24.5, 24.7, 24.19
12/2 27. Congruence Modulo m 27.1 , 27.2, 27.8 , 27.11, 27.12, 27.13, 27.15, 27.18
Week 16
12/7 27. The GCD, the Euclidean Algorithm, Modular Inverses 27.5, 27.7, 27.9 , 27.10, 27.16, 27.19, 27.20 , 27.21
12/11 Final Exam - Friday, December 11, 12:30-2:30 p.m. (cumulative)