CSE 20: Discrete Mathematics (Winter, 2006)

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Homework

Homework is essential to understanding and learning the material. Exams will be similar to the homework problems. Homework will be assigned, but will not be collected or graded. If you'd like your homework to be graded, turn it in to one of the TAs or the Instructor.

The quizzes will be at the beginning of class each Thursday, except for the first week and the day of the first midterm. Each quiz will consist of slight modifications to several of the homework problems assigned for that day (covering material from the previous week). For example, the quiz on January 19th (Day 4), will be comprised of slight modifications to several of the homework problems assigned for that day (covering material from the first week of class).

These assignments are a minimum; you'll be well-rewarded by doing additional problems. You need to have lots of practice in solving problems. Consider doing all review problems in Bender, and selected problems from Schaum's 2000 Solved Problems in Discrete Mathematics.

There are corrections to the Bender book. I suggest you markup your book with the corrections immediately.

Day homework is due Homework Homework solutions
January 20 (Day 4)
  • BF:1.3, 1.5, 1.13, 1.15, 2.3, 2.6, 2.7 (answer to 2.7 in book is wrong)
  • Modify the half-adder circuit to use only AND, OR, and NOT gates.
  • Solow: 1.4, 1.5, 2.15, 2.18, 2.19, 2.22
Homework
Quiz

January 27 (Day 6)
  • BF:2.9, 2.10, 2.13, 2.15, 2.16
  • LO: 1.7, 1.10, 1.16 (why or why not?), 1.23
  • Solow: 3.7, 3.11, 3.15, 4.6, 4.11, 9.3, 9.7, 9.8, 9.17
Homework
Quiz

February 2 (Day 8) The homework set will not be tested on a quiz, but will be good practice for the first midterm.
  • LO: 2.8, 2.14, 2.18, 2.19, Review Questions 7, 9
  • NT: 1.3, 1.8 1.11, 1.17
  • Solow: 5.2, 5.7, 5.14
Homework

February 9 (Day 10)
  • What is the product of gcd(a,b) and lcm(a, b). Give an explanation using the prime factorization of a and b.
  • What is the check-digit of the ISBN whose first nine digits are 156592856?
  • If I give you a purported ISBN and ask whether it is valid, explain what possible answers you can provide by verifying the check digit (yes, no, maybe)?
  • Which of the following are possible answers to the problem 1238423487234 * 230498230498234 and why?
    1. 285454422418489283558544756
    2. 285454422414889283558544756
    3. 285454422414889273558544756
    4. 285454425414889283558544756
  • NT:2.1
Homework
Quiz
February 16 (Day 12)
  • SF 1.2, 1.3, 1.6 (specializing the sets means to give specific sets as counterexamples), 1.9
  • Solow: 5.15
Homework
Quiz

February 23 (Day 14)
  • SF:1.15, 1.16, 1.19, 1.20, 2.4, 2.6, 2.9, 2.12.
    Prove using the element method that, for all subsets, P, Q, R of U, Q-(P ∩ R) = Q-(P ∩ Q ∩ R)
Homework
Quiz

March 9 (Day 18)
  • IS:1.7, 1.16, 1.4 (Prove 1.4 twice, once by induction, and the second time using the perturbation method. Hint for the perturbation method: you might find it useful to use the perturbation method with a summand of k^3 rather than k^2).
  • All pumpkins are the same weight; we can prove this by induction on the number of pumpkins in a given set. Here's how:
    If there's just one pumpkin then it's the same weight as itself, so the basis is trivial. For the induction hypothesis, assume that there are n pumpkins numbered 1 to n. By the induction hypothesis, pumpkins 1 through n-1 are the same weight, and similarly pumpkins 2 through n are the same weight. But the middle pumpkins, 2 through n-1 can't change weight when they're in different groups. So pumpkins 1 and n must be the same weight as well, by transitivity. Thus all n pumpkins are the same weight; QED.
    What, if anything, is wrong with this reasoning?
  • The following are true for the predicate P:
    • P(2)
    • P(n) -> P(n-1) (for n >= 1)
    • (P(2) AND P(n)) -> P(2n)
    Show by induction that P(i) is true for all non-negative integers i.
  • IS:2.1, 2.2, 2.3.
  • IS Review questions: 1, 2, 4, 7
Homework
Quiz

March 16 (Day 20)
  • IS:Review questions: 10, 11
  • EO:1.5, 1.10, 1.15, 1.22
  • In a group of 30 people, must at least 3 have been born in the same month. Why?
  • In a group of 30 people, must at least 4 have been born in the same month. Why?
  • A programmer writes 500 lines of computer code in 17 days. Must there have been at least one day when the programmer wrote 30 or more lines of code. Why?
  • Let S be a set of ten integers chosen from 1 through 50. Show that the set contains at least two different (but not necessarily disjoint) subsets of four integers that add up to the same number. (For instance, if the ten numbers are {3, 8, 9, 18, 24, 34, 35, 41, 44, 50}, the subsets can be take to be {8, 24, 34, 35} and {9, 18, 24, 50}. The numbers in both of these add up to 101.)
Homework
Quiz

March 24 (Final Exam)
    These questions are good practice for the final exam.
  • EO:2.1, 2.16, 2.22, 2.23