This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Econ 3190 Fall 2011 HW#2 Solution 1. #2.26 (a) If the person violates all 7 rules, then he or she has to pick 5 rules out of 7 to follow, which is C 5 7 = 21 (b) If the person has already followed 2 health rules, then he or she has to pick 3 more rules out of the remaining 5 to follow, which is given by C 3 5 = 10 2. #2.31 (a) The police needs to &nd 2 di/erent digits which can be given by N = 9 & 8 = 72 : Because we know that the number 5 has already be chosen. Then there are only 9 choices for the &rst missing number and 8 for the next. 3. #2.32 (a) P 6 6 = 6 & 5 & 4 & 3 & 2 & 1 = 720 (b) In this question, we need to consider the three speci&c persons as a new group or a new person . Then we have to &rst arrange the 4 persons by P 4 4 and then consider the order of those three speci&c persons which is P 3 3 . Then the answer is P 4 4 & P 3 3 = 4 & 3 & 2 & 1 & 3 & 2 & 1 = 144 (c) We know that there are 720 ways to arrange these 6 people if there is no special request. If 2 persons refuse to follow each other, then we just need to subtract the cases when these 2 persons stay together. Then the answer is given by P 6 6 P 5 5 & P 2 2 = 720 240 = 480 , where P 5 5 P 2 2 gives the ways to arrange these 6 people if those 2 persons follow each other. 4. #2.33 (a) For each question, the student should pick one answer from 4 possible answers, which is C 1 4 . And there are 5 questions in total, that is C 1 4 C 1 4 C 1 4 C 1 4 C 1 4 = 4 5 = 1024 (b) Since there are 3 possible incorrect answers for each question, the student must always choose from one of the three incorrect answers to get all answers wrong, that is C 1 3 C 1 3 C 1 3 C 1 3 C 1 3 = 3 5 = 243 5. (a) First pick 2 experts from 5 experts, then 4 workers from 6 workers.5....
View
Full
Document
This note was uploaded on 11/30/2011 for the course ECON 3190 at Cornell University (Engineering School).
 '07
 HONG

Click to edit the document details