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Workers/Machine Jobs: Assignment Problems

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Assignment problems

Workers/Machine Jobs
1 A
2 B
3 C
4 D

Workers Jobs
A B C D
1 10 8 7 12
2 9 7 13 17
3 6 7 8 9
4 11 2 5 10
m=n
Assign the jobs for the workers so that the total processing time is minimum.

Jobs
Men
I II III IV V
A 9 22 58 11 19
B 43 78 72 50 63
C 41 28 91 37 45
D 74 42 27 49 39
E 36 11 57 22 25

Since the number of rows is equal to Number of columns in the cost matrix,
the given assignment problem is balanced.

Row
min
9 22 58 11 19 9
43 78 72 50 63 43
41 28 91 37 45 28
74 42 27 49 39 27
36 11 57 22 25 11

Select the smallest cost element in each row and subtract this from all the
elements of the corresponding row, we get the reduced matrix

0 13 49 2 10
0 35 29 7 20
13 0 63 9 17
47 15 0 22 12
25 0 46 11 14
Select the smallest cost element in each column and subtract this from all the
elements of the corresponding column,

0 13 49 2 10
0 35 29 7 20
13 0 63 9 17
47 15 0 22 12
25 0 46 11 14
Column 0 0 0 2 10
min
we get the reduced matrix:

cover all the zeros by drawing a minimum number of lines.

0 13 49 0 0
0 35 29 5 10
13 0 63 7 7
47 15 0 20 2
25 0 46 9 4

0 17 49 0 0
0 39 29 5 10
9 0 59 3 3
47 19 0 20 2
21 0 42 5 0
I II III IV V
A 0 17 49 0 0
B 0 39 29 5 10
C 9 0 59 3 3
D 47 19 0 20 2
E 21 0 42 5 0

Jobs
Men
I II III IV V
A 9 22 58 11 19
B 43 78 72 50 63
C 41 28 91 37 45
D 74 42 27 49 39
E 36 11 57 22 25

Minimum processing time:


Determine the optimum assignment schedule.

I II III IV V
A 8 4 2 6 1
B 0 9 5 5 4
C 3 8 9 2 6
D 4 3 1 0 3
E 9 5 8 9 5

I II III IV V
A
B
C
D
E

I II III IV V
A
B
C
D
E

I II III IV V
A
B
C
D
E
MAS company has four jobs to be assigned to 5 machines. Only one job could
be assigned to one machine. The amount of time in hours required for the jobs
in machine are given in the following matrix.

Machines
Job
A B C D E
1 4 3 6 2 7
2 10 12 11 14 16
3 4 3 2 1 5
4 8 7 6 9 6

Find the optimum assignment of jobs to the machines to minimize the


total processing time and also find for which machine no job is assigned. What
is the total processing time to complete all the jobs.

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