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Basic Optimization - Define and Solve a Problem

1. Click the Solver command to display the Solver parameters dialog.

2. In the Target cell box, enter a cell reference or name for the objective cell. The objective cell must contain a formula.

Do one of the following:

  • If you want the value of the objective cell to be as large as possible, click Maximum.
  • If you want the value of the objective cell to be as small as possible, click Minimum.
  • If you want the objective cell to be a certain value, click Value Of, and then type the value in the box or select a cell which contains a number.

    If you leave the Target cell box empty, the "input cell empty" message will be shown.

    3. In the By Changing Cells box, enter a name or reference for each decision variable cell. To have an effect, the variable cells must be related directly or indirectly to the objective cell, or to the cell reference in at least one constraint.

    4. In the Limiting conditions field, enter any constraints that you want to apply. To add a constraint: In the Solver dialog box, under Limiting conditions, click in the Cell Reference box, enter the cell reference or name of the cell range whose value(s) you would like to constrain.  You can use a single cell or a cell range, but not multiple ranges.

    5. Click the relationship ( <=, =, >=, int, bin,) in the Operator box, that you want between the referenced cell(s) and the constraint.

    • If you click int, integer appears in the constraint box.
    • If you click bin, binary appears in the constraint box.

    In the constraint box, type a number, a cell reference or name, or a formula. For best performance and best results use a number, or a reference or name of a cell or cells that contain numbers.

    6. In the Value box you can enter the cell reference or name of the cell range whose value(s) you want to constrain as well.

    7. If it is necessary, you can change the existing constraint parameters by clicking again or delete with using the deleting field in the right side of the dialog box.

    8. By clicking Options, for simplicity you may select the Assumed Variables Non-Negative check box to specify that all decision variable cells without explicit lower bounds should be given lower bounds of zero.

    9. A constraint such as A1:A5 = integer, where A1:A5 are decision variable cells, requires that the solution values for A1 through A5 must be integers or whole numbers, such as -1, 0 or 2, to within a small tolerance (determined by the Options). Integer constraints may be used when a fractional solution value, such as 1.5, wouldn’t make sense in your problem – for example, if the decision variable represents how many people to schedule or how many trucks to buy.

    10. A constraint such as A1 = binary is equivalent to specifying A1 = integer, A1 >= 0 and A1 <= 1. This implies that A1 must be either 0 or 1 at the solution; hence A1 can be used to represent a "yes/no" decision, such as whether or not to build a new manufacturing plant.

    11. Click Solve and in the Solving Result dialog box, read the message and after reading these messages, do one of the following:

    • To keep the final values in the decision variable cells, click Keep Result.
    • To restore the values of the decision variable cells at the time you clicked Solve, click Restore Previous.
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