MYP Maths: Whole Numbers & Operations FAQ

It's the MYP 1-3 unit covering the set of whole numbers (0, 1, 2, 3…), place value, and the four operations — addition, subtraction, multiplication and division — plus order of operations, factors, multiples, primes and integers. It builds the number sense every later MYP and DP topic assumes you already have.

Whole numbers are 0, 1, 2, 3… with no negatives and no fractions. Integers include those same numbers plus their negatives: …-3, -2, -1, 0, 1, 2, 3… Every whole number is an integer, but not every integer is a whole number — that's the exact line examiners check students understand.

Because without an agreed order, the same expression gives different answers to different people — maths stops being reliable. IB classrooms use BIDMAS (Brackets, Indices, Division/Multiplication, Addition/Subtraction) or the equivalent PEMDAS; both mean the same thing, just different acronyms for the same fixed order.

In fifteen years of marking MYP work, the same three errors show up constantly: misapplying order of operations, sign errors when subtracting negatives, and confusing factors with multiples. All three are fixable with deliberate practice, not talent — they're habits, not gaps in ability.

Almost always it's a sign-handling slip, not a conceptual gap — students forget that subtracting a negative is the same as adding, or that multiplying two negatives gives a positive. Practise the sign rules as a standalone drill for ten minutes before tackling mixed questions; it isolates the actual error.

Use prime factorisation: break both numbers into their prime factors, then the HCF (Highest Common Factor) is the product of shared primes at their lowest power, and the LCM (Lowest Common Multiple) is the product of all primes at their highest power. It's slower than guessing but never wrong.

It's mostly assessed through Criterion A (Knowing and Understanding) — applying correct operations and mathematical reasoning to solve problems — and sometimes Criterion C (Communicating), where students must show clear, logical working. Schools set their own unit tests; there's no single external MYP exam for this topic.

Show every step, don't skip working even when a calculation feels obvious, and always state your answer in context — units, correct rounding, and whether the value makes sense. Criterion A rewards accurate, justified reasoning; a correct answer with no working rarely earns full marks.

After whole numbers and operations, MYP 1-3 typically moves into fractions, decimals and percentages, then ratio and proportion, followed by algebraic expressions and equations. Number sense from this unit underpins all of them — weak foundations here tend to resurface as algebra mistakes two years later.

Not conceptually hard, but it's foundational — gaps here quietly cause bigger problems in algebra and DP-level Maths AA or AI later on. Most students who struggle aren't lacking ability; they've never had the four operations and order of operations drilled to automatic fluency.

Short, frequent, no-calculator practice beats long weekend sessions — ten minutes on mental arithmetic, sign rules and order of operations most days builds the automaticity this topic needs. Ask them to explain their working out loud; if they can teach it back to you, they've actually understood it.