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ID: 3147499 • Letter: H
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home / study / business / operations management / operations management questions and answers / 4.a. a small auto-repair shop has six cars in for repair. only repairman murat usta is available ...
Question: 4.a. A small auto-repair shop has six cars in for repair. Only repairman Murat Usta is available ...
4.a. A small auto-repair shop has six cars in for repair. Only repairman Murat Usta is available to do repairs. He
estimates the following times needed to repair cars.
Car
1
2
3
4
5
6
Repair Time (minutes)
115
145
40
25
70
30
(a) Suppose that the cars’ owners are waiting in the rest room of the repair shop, and each car owner will leave the
shop when his/her car is finished. Furthermore, Murat Usta serves tea and cookies to his customers and this
costs him $6 per customer per hour of customer waiting time. Which sequence to repair the cars would you
recommend Murat Usta to follow?
home / study / math / statistics and probability / statistics and probability questions and answers / 4.b. a small auto-repair shop has six cars in for repair. only repairman murat usta is available ...
Question: 4.b. A small auto-repair shop has six cars in for repair. Only repairman Murat Usta is available ...
4.b. A small auto-repair shop has six cars in for repair. Only repairman Murat Usta is available to do repairs. He
estimates the following times needed to repair cars.
Car
1
2
3
4
5
6
Repair Time (minutes)
115
145
40
25
70
30
(b) Suppose that each car owner leaves the shop without waiting in the rest room of the repair shop. Murat Usta
will call car owners when all cars are finished. Furthermore, Murat Usta decides to hire the repairman, whose
name is Mehmet Usta and his repair speed is same as Murat Usta. Apply the First-Fit Decreasing (FFD)
algorithm to develop a schedule to recommend Murat Usta to complete all car repairs in a shortest possible
time.
home / study / business / operations management / operations management questions and answers / 4.c. a small auto-repair shop has six cars in for repair. only repairman murat usta is available ...
Question: 4.c. A small auto-repair shop has six cars in for repair. Only repairman Murat Usta is available ...
4.c. A small auto-repair shop has six cars in for repair. Only repairman Murat Usta is available to do repairs. He
estimates the following times needed to repair cars.
Car
1
2
3
4
5
6
Repair Time (minutes)
115
145
40
25
70
30
(c) Suppose that each car owner leaves the shop without waiting in the rest room of the repair shop. MuratUsta
will call car owners when all cars are finished. Furthermore, Murat Usta decides to hire the repairman, whose
name is Mehmet Usta and his repair speed is twice as fast as Murat Usta. Apply the First-Fit Decreasing (FFD)
algorithm to develop a schedule to recommend Murat Usta to complete all car repairs in a shortest possible
time.
Car
1
2
3
4
5
6
Repair Time (minutes)
115
145
40
25
70
30
Explanation / Answer
(4) (a) we can use FIRST FIT DECREASING ORDER but waiting cost of customers not suitable to use this
hence a better solution is to minimise no. of waiting customers and use first fit increasing order i.e.
car requiring minimum time. sheduling is given below :-
4th car (25 minutes) , 6th car (30 minutes) ,3rd car(40 minutes) ,5th car( 70 minutes) 1st car( 115 minutes)
and 2nd car( 145 minutes). This shedule will decrease no. of customer after 25 minutes 5, after 55 minutes
4 and so on.
(b) now no customer is waiting hence now FFD model suitable.again two workers available with same working
speed i.e. working shedule will be given as
MURAT USTA MEHMAT USTA
2nd car (145 minutes) 1st car( 115 minutes)
3rd car ( 40 minutes) 5th car (70 minutes)
6th car (30 minutes) 4th car (25 minutes)
TOTAL TIME REQUIRED 215 MINUTES FOR MURAT AND 210 FOR MEHMAT SHOTTEST TIME
(C) again no cost of customers waiting time hence FFD is suitable.again given that mehmat is twice faster than
murat hence shedule is given as
MEHMAT USTA MURAT USTA
2nd car( 145 minutes / 2) 1st car ( 115 minutes)
5th car (70 minutes/2) 6th car (30 minutes)
3rd car (40 minutes/2)
4th car ( 25 minutes/2) as MEHMAT SPEED IS DOUBLE OF MUTAT ,MEHMAT CAN WORK ON 2ND
5TH, 3RD AND 4TH USING FFD AS MURAT WILL BE BUSY ON1ST AND 6TH
TOTAL POSSIBLE TIME FOR MEHMAT = 72.5+35+ 20 +12.5 = 140 MINUTES
AND FOR MURAT = 115 + 30 = 145 MINUTES
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