Primary 1 addition and subtraction covers the concepts themselves, the +, − and = symbols, the relationship between the two operations, adding more than two 1-digit numbers, working within 100, standard algorithms, and mental calculation.
What addition and subtraction actually asks of a Primary 1 student
Two things are happening at once in this topic, and only one of them is arithmetic. The first is getting answers right. The second, which matters far more later, is understanding that addition and subtraction are opposites — that if 7 + 5 = 12 then 12 − 5 must be 7, without recalculating.
That relationship is what lets a child check their own work, and later it is what makes algebra possible. A student who has never internalised it will spend years solving equations by trial rather than by reversing an operation.
What the syllabus covers
Under the MOE primary mathematics syllabus, addition and subtraction at Primary 1 covers:
- concepts of addition and subtraction
- use of +, − and =
- relationship between addition and subtraction
- adding more than two 1-digit numbers
- adding and subtracting within 100
- adding and subtracting using algorithms
- mental calculation within 20, of a 2-digit number and ones without renaming, and of a 2-digit number and tens
Where the marks actually go
Renaming, or what most parents call carrying and borrowing, is where the year’s marks sit. A child who has learned the procedure without understanding that ten ones become one ten will apply it in the wrong direction under pressure.
Adding more than two single digits catches out children who can only add in pairs and lose track of the running total. This is a working-memory issue, not a mathematical one, and it improves with a written intermediate step.
Mental calculation questions are often treated as optional practice. They are not: the syllabus specifies them, and speed with 2-digit-and-tens is what makes Primary 2 arithmetic feel manageable rather than exhausting.
How to practise this properly
Ask for the matching subtraction after every addition fact, and the reverse. Two questions instead of one, and the second one is where the understanding forms.
When renaming is shaky, go back to bundles of ten physically before returning to the written algorithm. The procedure is much easier to remember once a child has seen why it works.
Keep mental calculation separate from written work — a few problems done aloud, with no pencil available. If a child reaches for paper to add 34 and 20, the mental strategies have not formed yet.
What this leads to
Primary 2 extends this to three-digit numbers and mental calculation with hundreds. Nothing new is introduced conceptually, which is exactly why a Primary 1 gap here becomes a Primary 2 problem rather than resolving itself.
It is also why a difficulty in one year is so often a leftover from an earlier one. Because our curriculum spans Primary 1 through Primary 6, we can go back to the genuine cause rather than treating the symptom in front of us. A child struggling with Primary 5 fractions frequently has a Primary 3 equivalence problem, and no amount of Primary 5 practice will resolve it.
What lessons at Odyssey are actually like
Here is a student talking about what studying with us is actually like. She is at secondary level; the teaching method is the one we use throughout, adjusted to the age. More are on Odyssey Math TV.
Getting help with this topic
We teach Primary 1 maths in small classes at Hexacube, 160 Changi Road #01-02, about three minutes from Eunos MRT. You can see our class schedules and fees, read about our math tutors, or look through the primary school math tuition programme as a whole. If your child is in a nearby school, our primary school directory may be useful too.
Start with the free trial lesson. We use it to work out where the difficulty really sits, and we will say so plainly — including if we think the sensible course is to wait a term and watch. Parents generally find that more useful than a confident sales answer. Get in touch or WhatsApp +65 8512 6882.
What we describe here comes from teaching this syllabus in our own classes since 2012. It is not a forecast for any individual child: progress is produced jointly, by a student willing to do the work with support at home. We do not promise grades. Topics follow the MOE primary mathematics syllabus — check the current syllabus on the MOE website for the definitive version, and see our curriculum page for how we teach it.
Frequently asked questions
Should my Primary 1 child memorise number bonds?
Fluency with bonds to 10 and then to 20 makes everything afterwards easier, but it should come from repeated use rather than flashcard drilling alone. A child who understands why 7 + 3 = 10 will recall it more reliably than one who has only memorised it.
Is it a problem if my child still counts on fingers?
At Primary 1 it is normal and not worth fighting. It becomes worth addressing if it is still the main strategy well into Primary 2, because by then the numbers are too large for it and it slows everything down.
What does “renaming” mean?
It is the modern term for carrying and borrowing — exchanging ten ones for one ten, or one ten for ten ones. The name changed to emphasise that the value stays the same and only its representation changes.
How do I know whether my child understands or has just memorised the steps?
Ask them to explain what they did to someone else. A child who understands can say why they crossed out the 4 and wrote 3; one who has memorised will only be able to repeat the action.
