Final answer:
The third step in the Problem-Solving Life Cycle (PLDC) is to identify exactly what needs to be determined in the problem, which involves identifying the unknown quantities and making a written list of these unknowns.
Step-by-step explanation:
After the problem has been clearly defined, the third step in the Problem-Solving Life Cycle (PLDC) is to identify exactly what needs to be determined in the problem; in other words, the step is to identify the unknown quantities. This step is crucial because it helps you to understand the problem in depth and lays out a clear path to the solution. To tackle complex problems effectively, it is often helpful to make a written list of the unknowns, as this will assist in organizing thoughts and ensuring that no critical aspects of the problem are overlooked.
Making a list of unknowns not only clarifies what you are solving for but can also guide the decision-making process as to what sequence the unknowns should be solved. This approach contributes significantly to the design of a systematic method for problem-solving.