数据、模型与决策(运筹学)课后习题和案例答案8..pdf

1、CHAPTER 8PERT/CPM MODELS FOR PROJECT MANAGEMENTReview Questions8.1-1 The bid is for$5.4 million with a penalty of$300,000 if the deadline of 47 weeks is not met.In addition,a bonus of$150,000 will be paid if the plant is completed within 40 weeks.8.1-2 He has decided to focus on meeting the deadline

2、 of 47 weeks.8.1-3 An immediate predecessor is an activity that must be completed just prior to starting the givenactivity.Given the immediate predecessors of an activity,this activity then becomes theimmediate successor of each of these immediate predecessors.8.1-4(1)the activities of the project;(

3、2)the immediate predecessors of the activities;and(3)theestimated duration of the activities8.2-1(1)activity information;(2)precedence relationships;and(3)time information(duration)8.2-2 In an AOA network,each activity is represented by an arc,while in an AON network,eachactivity is represented by a

4、 node.AON networks are being used here.8.2-3 The bars in a Gantt chart show the scheduled start and finish times for activities in a project.8.3-1(a)A path through a project network is one of the routes following the arrows(arcs)from thestart node to the finish node;(b)the length of a path is the su

5、m of the estimated durations ofthe activities on the path;(c)the longest path is called the critical path.8.3-2(1)The actual duration of each activity must be the same as its estimated duration;and(2)each activity must begin as soon as all its immediate predecessors are finished.8.3-3 The earliest s

6、tart time of an activity is equal to the largest of the earliest finish times of itsimmediate predecessors.8.3-4 A forward pass is the process of starting with the initial activities and working forward in timetoward the final activities.8.3-5 It is a last chance schedule because anything later will

7、 delay the completion of the project.8.3-6 The latest finish time of an activity is equal to the smallest of the latest start times of itsimmediate successors.8.3-7 A backward pass starts with the final activities and works backward in time toward the initialactivities instead of starting with the i

8、nitial activities.8.3-8 Any delay along the critical path will delay project completion.8.3-9(1)Identify the longest path through the project network;and(2)identify the activities withzero slack-they are on the critical path.8.4-1 The three estimates are the most likely estimate,optimistic estimate,

9、and pessimistic estimate.8-18.4-2 The optimistic and pessimistic estimates are meant to lie at the extremes of what is possible,whereas the most likely estimate provides the highest point of the probability distribution.8.4-3 It is assumed that the mean critical path will turn out to be the longest

10、path through the projectnetwork.8.4-4 It is assumed that the durations of the activities on the mean critical path are statisticallyindependent.8.4-5|ip=sum of the means of the durations fbr the activities on the mean critical path.8.4-6 ap2=sum of the variances of the durations for the activities o

11、n the mean critical path.8.4-7 It is assumed that the form of the probability distribution of project duration is the normaldistribution.8.4-8 It is usually higher than the true probability.8.5-1 Using overtime,hiring additional labor,and using special materials or equipment are all waysof crashing

12、an activity.8.5-2 The two key points are labeled normal and crash.The normal point shows the time and cost ofthe activity when it is performed in the normal way.The crash point shows the time and costwhen the activity is fully crashed.8.5-3 No,only crashing activities on the critical path will reduc

13、e the duration of the project.8.5-4 Crash costs per week saved are being examined.8.5-5 The decisions to be made are the start time of each activity,the reduction in the duration ofeach activity due to crashing,and the finish time of the project.8.5-6 An activity cannot start until its immediate pre

14、decessor starts and then completes its duration.8.5-7 Because of uncertainty,the plan fbr crashing the project only provides a 50%chance ofactually finishing within 40 weeks,so the extra cost of the plan is not justified.8.6-1 PERT/Cost is a systematic procedure to help the manager plan,schedule,and

15、 control projectcosts.8.6-2 It begins by developing an estimate of the cost of each activity when it is performed in theplanned way.8.6-3 A common assumption is that the costs of performing an activity are incurred at a constant ratethroughout its duration.8.6-4 A work package is a group of related

16、activities.8.6-5 PERT/Cost uses earliest start time and latest start time schedules as a basis for developing costschedules.8.6-6 A PERT/Cost schedule of costs shows the weekly project cost and cumulative project cost foreach time period.8.6-7 A PERT/Cost report shows the budgeted value of the work

17、completed of each activity and thecost overruns to date.8-28.6-8 Since deviations from the planned work schedule may occur,a PERT/Cost report is needed toevaluate the cost performance of individual activities.8.7-1 Planning,scheduling,dealing with uncertainty,time-cost trade-offs,and controlling cos

18、ts areaddressed by PERT/CPM.8.7-2 Computer implementation has allowed fbr application to larger projects,faster revisions inproject plans and effortless updates and changes in schedules.8.7-3 The accuracy and reliability of end-point estimates are not as good for points that are not at theextremes o

19、f the probability distribution.8.7-4 The technique of computer simulation to approximate the probability that the project will meetits deadline is an alternative fbr improving on PERT/CPM.8.7-5 The Precedence Diagramming Method has been developed as an extension of PERT/CPM todeal with overlapping a

20、ctivities.8.7-6 PERT/CPM assumes that each activity has available all the resources needed to perform theactivity in a normal way.8.7-7 It encourages effective interaction between the project manager and subordinates that leads tosetting mutual goals for the project.8.7-8 New improvements and extens

21、ions are still being developed but have not been incorporatedmuch into practice yet.8-3Problems8.1 a)b)Start-A f C FinishStart f A f D f E FinishStart B f C f FinishStart B D-E FinishLength=4 weeksLength=7 weeksLength=5 weeksLength=8 weeks*critical pathc)ActivityESEFLSLFSlackCritical PathStart00000Y

22、esA02131NoB03030YesC35683NoD35350YesE58580YesFinish88880YesCritical Path:Start f B D E f Finishd)No,this will not shorten the length of the project because the activity is not on the criticalpath.8-48.2 a)b)Start f A D FinishStart-A-E-FinishStart A f F K f FinisStart f G-H f I f J f FinishStart-B-D

23、FinishStart-B-C E FinishStart B C f H 1 J FinishStart B C f K FinishLength=4 weeksLength=5 weeksLength=8 weeksLength=8 weeksLength=3 weeksLength=6 weeksLength=8 weeksLength=7 weeks*critical pathcritical pathcritical path8-5C)ActivityESEFLSLFSlackCritical PathStart00000YesA02020YesB01010YesC13130YesD

24、24684NoE36582NoF24240YesG23230YesH34340YesI45450YesJ58580YesK48480YesFinish88880YesCritical Paths:Start A-F-K FinishStart A G H I J T FinishStart-B C H 1 J-Finishd)No,this will not shorten the length of the project because A is not on all of the criticalpaths.8-68.3 a)8-7b,c,&d)ActivityESEFLSLFSlack

25、Critical PathStart00000YesA01010YesB13130YesC37370YesD36360YesE35461NoF7107100YesG6116110YesH101110110YesI111511150YesJ151715170YesK151816191NoL172017200YesM182319241NoN202420240YesFinish242424240YesCritical Paths:Start A fB -C F f H I f J-L N FinishStart-A B-D G-I J-L N Finish8-88.4 a)b)Start A B f

26、 J-L FinishStart C FinishStart f E f F J-L-FinishStart G J L FinishStart K f L FinishLength=75 minutesLength=45 minutesLength=72 minutesLength=67 minutesLength=45 minutes*critical path8-9Critical Path:Start-A B Finishd&e)ActivityESEFLSLFSlackCritical PathStart00000YesA0300300YesB303530350YesC0230323

27、0NoD2532353()NoE073103NoF73210353NoG0158238NoH152523338NoI252733358NoJ354535450YesK01530453()NoL457545750YesFinish757575750Yesf)Dinner will be delayed 3 minutes because of the phone call.If the food processor is usedthen dinner will not be delayed because there was 3 minutes of slack and 5 minutes o

28、fcutting time saved and the call only used 6 minutes of the 8 total.8.5a)Start A f D-H M FinishStart f J-M FinishStart C F-K fN FinishStart f A f I M f FinishStart f C G f L-N FinishLength=19 weeksLength=20 weeks*critical pathLength=16 weeksLength=17 weeksLength=20 weeks critical path8-10b)ActivityE

29、SEFLSLFSlackCritical PathStart00000YesA06171NoB03030YesC04040YesD6107111NoE3103100YesF488124NoG4104100YesH101311141NoI6119143NoJ1()1410140YesK81112154NoL101510150YesM142014200YesN152015200YesFinish202020200YesKen will be able to meet his deadline if no delays occur.c)Critical Paths:Start f B E J M F

30、inishStart f C G f L-N-FinishFocus attention on activities with 0 slack(those in the critical paths).d)If activity I takes 2 extra weeks there will be no delay because its slack is 3.If activity Htakes 2 extra weeks then there will be a delay of 1 week because its slack is 1.If activity Jtakes 2 ext

31、ra weeks there will be a delay of 2 weeks because it has no slack.8-118.6 a)b)ActivityESEFLSLFSlackCritical PathStart00000YesA05050YesB01111211NoC13121411NoD597112NoE5115110YesF111411140YesFinish141414140YesCritical Path:Start A f E-F FinishLength=14 monthsc)6 months8-128.7ActivityESEFLSLFSlackCriti

32、cal PathStart00000YesA03030YesB3113110YesC112911290YesD293929390YesE293430351NoF344435451NoG3950395()0YesH506750670YesI293836457NoJ445345541NoK535757614NoL536054611NoM677067700YesN606961701NoFinish70707()7()0YesCritical Path:Start f A f B C f D-G f H f M FinishTotal duration=70 weeks8.8ActivityESEFL

33、SLFSlackCritical PathStart00000YesA01010YesB13130Yesc39390YesD91311152NoE91()91()0YesF1()1410140YesG131815202NoH182320252NoI91211142NoJ141714170YesK172117210YesL171820213NoM232425262NoN212621260YesFinish262626260YesCritical Path:Start A-B C-E K N f FinishTotal duration=26 weeks8-138.9Total duration=28 weeksActivityESEFLSLFSlackCritical PathStart00000YesA01010YesB13130YesC31()31()0YesD101413173NoE1