Solving a maths problem includes checking whether the information is sufficient. Sometimes a difficult answer reveals a missing idea in the learner's understanding. Sometimes the question has left something out.
Consider a rectangular garden with a perimeter of twenty metres. What is its area? A rectangle measuring one metre by nine metres has the stated perimeter and an area of nine square metres. A four-by-six-metre rectangle has the same perimeter and an area of twenty-four square metres.
Show why the answer is not unique
Both examples satisfy the question, so the perimeter alone cannot establish a single area. If the garden is also specified as square, each side is five metres and the area is twenty-five square metres. The extra condition changes what can be concluded.
Ask a learner to draw two examples that fit a problem's information. Label the dimensions and units, then check each calculation. If the results differ, identify the missing condition rather than choosing the answer that looks more plausible.
Now reverse the exercise. Write a question with just enough information for another person to solve it. Ask them to explain any assumptions they made. If their interpretation differs from yours, revise the wording and try again.
Questioning a problem still requires reasoning. A worked counterexample is stronger than an objection to the available options. Equally, a printed answer should be checked when it conflicts with a sound demonstration.
The goal is a clear account of what follows from the information given. Being precise about assumptions is part of mathematics, and a useful habit wherever a confident answer rests on an incomplete question.