ECS20 TA Website


This is the Spring 2007 teacher assistant website for ECS20. You'll find general information regarding office hours, grading, and the discussion sections here.

The main course website is located here. Homeworks are posted on the main course website.

Latest News

[ 04 June 2007 ]
I posted scores and solutions on for homework 9. Good luck on the final!

[ 04 June 2007 ]
I posted scores and solutions on for homework 8 last night.

[ 01 June 2007 ]
I've posted the homework notes from today's discussion. Good luck!

[ 29 May 2007 ]
Homework 7 is finally graded! Scores and solutions are on

CHECK YOUR GRADES! If you have a zero listed anywhere, I did not receive or grade that homework. Please make sure this is correct!

[ 27 May 2007 ]
Have a great Memorial Day weekend! I don't have which problems to grade yet, so don't expect homework 7 to be graded until sometime next week.

[ 25 May 2007 ]
Discussion slides from today have been posted. Good luck on the homework!

[ 22 May 2007 ]
Phew! Homework 6 is graded. Scores are up at I'll hand back your homework (complete with a new point breakdown) during Friday's discussion.

[ 21 May 2007 ]
Since John will be gone, I will be holding extra office hours this week to help with any homework questions. In addition to my normal Wednesday office hours, you can find me on Tuesday from 8:00pm - midnight in Kemper Hall room 53.

Also, I'll be monitoring the newsgroups every night this week. Please post your homework questions there! If you are unable to make office hours and have tried using the newsgroups but still need help, please feel free to email me. I might be able to arrange another short time slot to help with a few questions.

[ 17 May 2007 ]
Since I will be out of town starting Friday, I will not finish grading homework 6 until early next week. However, I did post the solutions to the graded problems on I'll include grading comments in next week's discussion section.

[ 13 May 2007 ]
Homework 5 scores and solutions have been posted on

[ 12 May 2007 ]
Here [pdf] are some notes to help with homework 6. I'll keep updating it with more information as more questions pop up on the newsgroups!

[ 09 May 2007 ]
Here [pdf] are some last minute notes to help with homework 5. (Earlier questions will lead to earlier posting of something like this!)

[ 05 May 2007 ]
Homework 4 scores and solutions have been posted on The averages for this homework were low, which isn't surprising considering the homework was due a day after the midterm. However, be sure you look back and understand how to do all of these problems. They will haunt you on the final!

I also posted slides for discussion 5. Keep in mind that these just outline the examples already provided in your book.

[ 29 April 2007 ]
Homework 3 scores and solutions have been posted on Good luck with the midterm!

[ 27 April 2007 ]
I finally finished a writeup on the solving systems of congruencies using the Chinese Remainder Theorem, along with information on how to reduce modulo m and find the modular inverse. I'm afraid I won't have time to provide any more examples before your midterm :( However, I should have some solutions for homework 3 up before Tuesday!

Slides for discussion 4 have been posted. An example using the Chinese Remainder Theorem to solve systems of congruencies will be posted tonite!

[ 22 April 2007 ]
Homework 2 grades have been posted on (Homework comments will be up by Tuesday.)

The mean score was 71.31% and the median was 70.83%. The following chart shows percents on the y-axis, and the number of students who scored below that on the x-axis. (Scores from students that did not turn in homework are not included.) The average is indicated by the red line.

[ 20 April 2007 ]
Slides for discussion 3 have been posted, along with the modular inverse example. Homework 2 will not be ready to hand back during discussion this time :( I'll have extra exercises up for the new sections by the end of Friday!

[ 17 April 2007 ]
I've created an online survey to get feedback regarding my performance and how to prioritize my time on what you find most important and useful. The responses are anonymous, so you can answer truthfully without worrying about repercussions. You can access the survey here.

Be sure to check the main course website. Homework due dates have been changed to Wednesday at 4pm!

[ 16 April 2007 ]
If you did not pick up your homework during discussion, I will have them in the TA office.

[ 13 April 2007 ]
Homework 1 grades have been posted on You may also find homework solutions on (accessible only by registered students).

Extra exercises and solutions have been posted for sections 2.1, 2.2, 2.3, and 2.4.

[ 11 April 2007 ]
I've updated the grading section with more submission requirements, like stapling your homework pages together. If you keep ignoring these requirements, I will start docking points!

[ 06 April 2007 ]
I posted today's (fixed) discussion notes and added the extra book exercises for section 1.3 Good luck on the homework!

[ 30 March 2007 ]
I've added a few more sections to this website, along with more information on the newsgroups and homework grading.

Please let me know if you have any trouble viewing the content on this website!