Learning solver functions using riddles

Introduction to solver

Solver us a computational service found in Excel. It's free and can be found in the Data tab of the ribbon. If you don't have it, you have to install it (also free). 

The solver interface is shown on the right. Let's understand its anatomy.

Set Objective: Reference one cell in your Excel sheet in this box - the answer cell. In most entrepreneurial applications, the objective cell references a mathematical function that maximizes π, revenue, or minimizes cost, time, or 𝛕.

By Changing Variable Cells: Reference the cell(s) that represent uncertain values. Typical variable cells in the entrepreneurial setting include: demand, price, customer arrival rates.

Subject to the Constraints: Solver is a wonderful tool when there is a lot of uncertainty about a business decision. Unfortunately, Solver isn't AI, so the "answers" it returns could be mathematically correct and unrealistic. To ensure that the answer found is both mathematically correct and realistic, add constraints.

Testing solver using a riddle

Take a look at the riddle on the left. It is structured in a way that a good entrepreneur would mimic when tackling a business situation which there are multiple uncertain variables. Developing mathematical relationships between variables can set you up for a successful solver-based solution.

Walk through the riddle above and correlate each of the 5 clues with the formulas in the main spreadsheet (above) or the clues in the constraints box (below).

Cell J63 (highlighted green) represents the second digit of the PIN and is the only digit on which all other digits have some form of relationship (direct or indirect). That cell will be our variable for which we want solver to solve.

Our objective will the 5th clue/constraint. The sum of all digits must equal 30.