Primary 4 covers adding and subtracting decimals up to 2 decimal places.
What adding and subtracting decimals actually asks of a Primary 4 student
The arithmetic is identical to whole numbers. Everything that goes wrong goes wrong because of where the digits are placed.
Aligning on the decimal point rather than on the right-hand digit is the single rule of this topic, and it contradicts four years of habit.
Children who did the Primary 3 money work carefully usually find this straightforward, because it is the same discipline with the dollar sign removed.
What the syllabus covers
Under the MOE primary mathematics syllabus, adding and subtracting decimals at Primary 4 covers:
- adding and subtracting decimals (up to 2 decimal places)
Where the marks actually go
Right-aligning instead of point-aligning, so 3.5 + 0.25 is computed as if the 5 and the 5 share a column.
Renaming across the decimal point handled incorrectly during subtraction.
The decimal point omitted from the answer entirely, turning 4.75 into 475.
How to practise this properly
Write the decimal points in a vertical line first, then fill in digits around them.
Pad with zeros so every number has the same number of decimal places. 3.5 becomes 3.50 and the columns become unambiguous.
Estimate with whole numbers before calculating, which catches misplaced points instantly.
Use squared paper. Alignment errors largely disappear when there is a grid to work in.
Practise subtraction where the top number has fewer decimal places than the bottom — 5 minus 2.35, for instance. Children stall here because there appears to be nothing to subtract from in the hundredths column, and padding with zeros resolves it instantly.
Mix decimal questions in with money questions in the same session. Seeing that $4.75 plus $2.60 and 4.75 plus 2.60 are the same calculation transfers the confidence children already have with money into a context where they often think they are less capable.
What this leads to
Multiplying and dividing decimals follows immediately at Primary 4, and Primary 5 applies all of it to measurement conversion and percentage.
Because each year assumes the last, we teach the primary levels as one continuous sequence. Our MOE-aligned curriculum covers Primary 1 through Primary 6, so repair happens at the source rather than at the surface. In practice that often means spending a lesson on something from two years ago in order to fix what is failing today.
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 4 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.
A free trial class costs you an hour and tells you where the real gap is. For most families that is more useful than another assessment book, because the problem is rarely a shortage of practice and usually a specific misunderstanding nobody has found yet. Book one here 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
What is the rule for adding decimals?
Line up the decimal points, not the right-hand digits. Everything else is ordinary addition.
Should I pad numbers with zeros?
It helps a great deal while the habit is forming. 3.5 written as 3.50 makes the columns obvious.
How many decimal places are examined?
Up to two for addition and subtraction at Primary 4.
Why does my child lose the decimal point?
Usually because it was never written in the working, only in the question. Writing it in every line of working prevents it.
