Study Problems for CS 173

Margaret Fleck, University of Illinois

This version was most recently updated in Fall 2015. Please report bugs to Margaret Fleck (

To get the full benefit out of these problems, you must write out your own solution to each BEFORE peeking at the model solution. Actually write it out, on paper, as if we were grading your answer. This will force you to think through the technical details and how to explain/justify your answer. If you cut corners on this process, you won't properly learn the material and you will do poorly on the exams.

For closely-related reasons, if you are using these solutions to help study for a different (e.g. not U. Illinois) course, use them in a sensible and honest manner. Use them as additional study aids, not as a place to copy answers to problems that you have been told to solve on your own.

Math prerequisites (e.g. logs and exponents)


(Simple Direct) Proofs

Number Theory

Modular Arithmetic

Set Theory




Two-way bounding


Finding closed forms



Collections of Sets

State Diagrams



Many of the problems in this collection are adapted from homework problems and solutions written by the CS 173 course staff at U. Illinois from Fall 2008 to Spring 2014.