Now we will add a variable to the model that describes the sum total of the work done for all tasks.
| Ø | Select the Variable tool. Click on the sketch below Work Done and type in the name total work done then press Enter. |
| Ø | Select the Arrow tool and click once on Work Done and then on total work done. |
| Ø | Open the Equation Editor on total work done. |
| Ø | Click on work done in the Variables list. |
When you do this it will be added with its subscript so that the equation will read:
total work done = work done[task]
This equation is not complete. If you were to check the model at this point you would get an error message saying task appears on the right but not the left. work done must contain the subscript task, but total work done does not require the subscript because it will add all the tasks together. For this, we use the SUM function.
total work done = SUM(work done[task!])
The exclamation point ! indicates which Subscript Range we want to sum over. In this case there is only one subscript, but there can be up to eight subscripts for a variable and it is important to indicate which subscripts the SUM function works on.
| Ø | Enter the SUM function and subscripts as they appear in the equation above. Enter the units drawing. Click on the checkbox Supplementary on the left hand side of the Equation Editor. Don't forget the exclamation mark ! Click OK. |
