The following questions were tested in PSLE Math papers around 5 and 10 years ago. Though this question type is not frequently tested in PSLE Math paper, questions like the above are frequently tested in school-based exam papers and a lot of Primary 4 to 6 students found themselves not able to understand and find a way to conquer this particular type of question.

Though easy to apply, it might not be easy to use Guess-and-Check to solve questions whereby numbers involved are big. A student might need to make many guesses before he can successfully “guess” the correct answer. A more efficient strategy, Assumption, was taught by many Math teachers and tutors to replace the conventional Guess-and-Check method.

This strategy is a non-routine heuristic that all pupils learn in primary schools. Many pupils learn how to use this strategy as early as when they were in primary two. In fact, the concept of working backwards is useful in many aspects of life, not just in solving Math problem sums.

In the previous article, I have shown you two strategies on Same Difference and Same Total. Today, I will continue to share with you two more key strategies that are often tested in school-based examinations or PSLE Math – Same Identity and Unchanged Variable.