7 Goal Seek and Solver

8/18/2019 7 Goal Seek and Solver

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Goal Seek and Solver


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Goal seeking helps you

Find a specific value for a target cell by

adjusting the value of one other cell whose

value is allowed to vary.


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1 On the Tools menu click Goal Seek.

! "n the Set cell bo# enter the reference for the

cell that contains the formula you want toresolve.

$ "n the To value bo# type the result you want.

% "n the &y changing cell bo# enter the

reference for the cell that contains the value you

want to adjust.


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Solver

Solver is given a specific target cell whose value is to be

' ma#imi(ed

' minimi(ed or

' made e)ual to a specific value.

"t is also given a set of cells whose value is to be

varied to accomplish the desired optimi(ation or

solution together with constraints on their values ifany.

Then it tries to obtain a solution by iteratively varying

the values of the variable cells.


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The cells you select must be related throughformulas on the worksheet.

"f not related changing one cell will notchange the other.

*s an e#ample Solver can be used to findthe best choice of advertising e#penditures

to generate ma#imum profit.


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+efine and solve a problem by

using Solver 1 On the Tools menu click Solver.

! "n the Set Target ,ell bo# enter a cell

reference or name for the target cell. Thetarget cell must contain a formula.


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$ To have the value of the target cell be as

large as possible click -a#.

To have the value of the target cell be assmall as possible click -in.

To have the target cell be a certain value

click alue of and then type the value inthe bo#.


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% "n the &y ,hanging ,ells bo# enter a name

or reference for each adjustable cell separating

nonadjacent references with commas.

The adjustable cells must be related directly orindirectly to the target cell.

/ou can specify up to !00 adjustable cells.

To have Solver automatically propose the

adjustable cells based on the target cell click

Guess.


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"n the Subject to the ,onstraints bo#enter any constraints you want to apply.

2 ,lick Solve. 3 To keep the solution values on the

worksheet click 4eep Solver Solution inthe Solver 5esults dialog bo#.

To restore the original data click 5estoreOriginal alues.


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Tip6

/ou can interrupt the solution process by

pressing 7S,. -icrosoft 7#cel recalculates the worksheet

with the last values found for the adjustable

cells.


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To add a constraint in Solver

1 On the Tools menu click Solver.

! ,lick *dd.

$ "n the ,ell 5eference bo# enter thereference or name of the cell range for

which you want to constrain the value.


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% ,lick the relationship 8 9: : ;: "nt or &in <that you want between the referenced cell and theconstraint.

"f you click "nt =integer= appears in the ,onstraint bo#.

"f you click &in =binary= appears in the,onstraint bo#.

"n the ,onstraint bo# type a number a cellreference or name or a formula.


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2 To accept the constraint and add another

click *dd.

To accept the constraint and return to theSolver >arameters dialog bo# click O4.


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?otes

/ou can apply the "nt and &in relationships

only in constraints on adjustable cells.


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@hen the *ssume Ainear -odel check bo#on the Solver Options dialog bo# isselected there is no limit on the number of

constraints. For nonlinear problems each adjustable cell

can have the following constraints6 a binary

constraintB an integer constraint plus upperlower or both limitsB or upper lower or both limitsB and you can specify an upper orlower limit for up to 100 other cells.


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,hange or delete a constraint in

Solver 1 On the Tools menu click Solver.

! "n the Subject to the ,onstraints bo#

click the constraint that you want to changeor delete.

$ To delete the constraint click +elete.

To change the constraint click ,hange and

then make the changes you want.


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Set Solver solution time and

iterations 1 On the Tools menu click Solver.

! ,lick Options.

$ "n the -a# Time bo# type the numberof seconds that you want to allow for the

solution time.

% "n the "terations bo# enter the ma#imumnumber of iterations that you want to allow.


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?otes

"f the solution process reaches the

ma#imum time or number of iterations

before Solver finds a solution Solverdisplays the Show Trial Solution dialog

bo#.


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Set the degree of precision and

convergence in Solver 1 On the Tools menu click Solver.

! ,lick Options.

$ "n the >recision bo# type the degree of precision that you wantB the smaller the

number the higher the precision.


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% "n the ,onvergence bo# type the

amount of relative change you want to

allow in the last five iterations beforeSolver stops with a solutionB the smaller the

number the less relative change that is

allowed.


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To set the tolerance in Solver

1 On the Tools menu click Solver.

! ,lick Options.

$ "n the Tolerance bo# type the percentage of error you want to allow in the

solution.


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@hen to start from different

initial solutions For nonlinear problems it can be helpful to

try different starting values for the

adjustable cells especially if Solver hasfound a solution that is significantly

different from what you e#pected.

/ou can also reduce the solution time by

setting the adjustable cells to values that you

suspect are close to optimal.


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For linear models 8that is when the *ssume

Ainear -odel check bo# on the Solver

Options dialog bo# is selected

7 Goal Seek and Solver

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