3. 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.
4. 1 On the Tools menu, click Goal Seek.
2 In the Set cell box, enter the reference
for the cell that contains the formula you
want to resolve.
3 In the To value box, type the result you
want.
4 In the By changing cell box, enter the
reference for the cell that contains the value
you want to adjust.
5.
6. Solver
Solver is given a specific target cell whose value is to
be
– maximized,
– minimized, or
– made equal to a specific value.
It is also given a set of cells whose value is to be
varied to accomplish the desired optimization or
solution, together with constraints on their values, if
any.
Then it tries to obtain a solution by iteratively varying
the values of the variable cells.
7. The cells you select must be related through
formulas on the worksheet.
If not related, changing one cell will not
change the other.
As an example, Solver can be used to find
the best choice of advertising expenditures
to generate maximum profit.
8.
9. Define and solve a problem by
using Solver
1 On the Tools menu, click Solver.
2 In the Set Target Cell box, enter a cell
reference or name for the target cell. The
target cell must contain a formula.
10. 3 To have the value of the target cell be as
large as possible, click Max.
To have the value of the target cell be as
small as possible, click Min.
To have the target cell be a certain value,
click Value of, and then type the value in
the box.
11. 4 In the By Changing Cells box, enter a name
or reference for each adjustable cell, separating
nonadjacent references with commas.
The adjustable cells must be related directly or
indirectly to the target cell.
You can specify up to 200 adjustable cells.
To have Solver automatically propose the
adjustable cells based on the target cell, click
Guess.
12. 5 In the Subject to the Constraints box,
enter any constraints you want to apply.
6 Click Solve.
7 To keep the solution values on the
worksheet, click Keep Solver Solution in
the Solver Results dialog box.
To restore the original data, click Restore
Original Values.
13. Tip:
You can interrupt the solution process by
pressing ESC.
Microsoft Excel recalculates the worksheet
with the last values found for the adjustable
cells.
14. To add a constraint in Solver
1 On the Tools menu, click Solver.
2 Click Add.
3 In the Cell Reference box, enter the
reference or name of the cell range for
which you want to constrain the value.
15. 4 Click the relationship ( <=, =, >=, Int, or Bin )
that you want between the referenced cell and the
constraint.
If you click Int, "integer" appears in the Constraint
box.
If you click Bin, "binary" appears in the
Constraint box.
5 In the Constraint box, type a number, a cell
reference or name, or a formula.
16. 6 To accept the constraint and add
another, click Add.
To accept the constraint and return to the
Solver Parameters dialog box, click OK.
17. Notes
You can apply the Int and Bin relationships
only in constraints on adjustable cells.
18. When the Assume Linear Model check box
on the Solver Options dialog box is
selected, there is no limit on the number of
constraints.
For nonlinear problems, each adjustable cell
can have the following constraints: a binary
constraint; an integer constraint plus upper,
lower, or both limits; or upper, lower, or
both limits; and you can specify an upper or
lower limit for up to 100 other cells.
19. Change or delete a constraint in
Solver
1 On the Tools menu, click Solver.
2 In the Subject to the Constraints box,
click the constraint that you want to change
or delete.
3 To delete the constraint, click Delete.
To change the constraint, click Change, and
then make the changes you want.
20. Set Solver solution time and
iterations
1 On the Tools menu, click Solver.
2 Click Options.
3 In the Max Time box, type the number
of seconds that you want to allow for the
solution time.
4 In the Iterations box, enter the maximum
number of iterations that you want to allow.
21. Notes
If the solution process reaches the
maximum time or number of iterations
before Solver finds a solution, Solver
displays the Show Trial Solution dialog
box.
22. Set the degree of precision and
convergence in Solver
1 On the Tools menu, click Solver.
2 Click Options.
3 In the Precision box, type the degree of
precision that you want; the smaller the
number, the higher the precision.
23. 4 In the Convergence box, type the
amount of relative change you want to
allow in the last five iterations before
Solver stops with a solution; the smaller the
number, the less relative change that is
allowed.
24. To set the tolerance in Solver
1 On the Tools menu, click Solver.
2 Click Options.
3 In the Tolerance box, type the
percentage of error you want to allow in the
solution.
25. When 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 has
found a solution that is significantly
different from what you expected.
You can also reduce the solution time by
setting the adjustable cells to values that
you suspect are close to optimal.
26. For linear models (that is, when the Assume
Linear Model check box on the Solver
Options dialog box is selected), the initial
values of the adjustable cells don't affect the
final values or the solution time.
