Singapore Mathematics | International Edition: Addition and Subtraction

Singapore Math addition and subtraction guide for families and teachers outside Singapore: what Primary 1 to Primary 3 students learn, how Singapore teaches it, and how to practise at home.

Addition and subtraction are taught as a pair.

Every subtraction fact is also an addition fact, seen from the other side.

In Singapore Mathematics, students add and subtract within 100 in Primary 1, with numbers up to 3 digits in Primary 2 and up to 4 digits in Primary 3. Mental calculation is listed at every one of these levels.

After Primary 3, addition and subtraction become tools inside fractions, decimals and measurement.

This guide is useful for families and teachers who want to:

• know the exact limits at each level;
• teach mental and written methods in a clear order;
• prepare a child who is moving into a Singapore school; or
• support a student using Singapore Math materials in another country.

---

What Addition and Subtraction Mean in Singapore Mathematics

Addition puts parts together to make a whole. Subtraction starts with the whole and finds a part.

Subtraction can mean taking away, comparing two amounts or finding a missing part. All three use the same calculation.

The syllabus names “the relationship between addition and subtraction” from Primary 1. If 8 + 5 = 13, then 13 − 5 = 8 and 13 − 8 = 5.

Singapore Math materials often show this part-whole idea as a number bond: a whole joined to its two parts. The Singapore Math Number Bonds guide explains the picture itself.

The written method depends on place value. When a column has ten or more ones, ten of them are renamed as one ten. When a column has too few, one ten is renamed as ten ones.

---

Where Addition and Subtraction Sit in the Singapore Syllabus

Level	Written methods	Mental calculation
Primary 1	Adding and subtracting within 100, including algorithms; adding more than two 1-digit numbers	Within 20; a 2-digit number plus ones without renaming; a 2-digit number plus tens
Primary 2	Algorithms up to 3 digits	A 3-digit number and ones, tens or hundreds
Primary 3	Algorithms up to 4 digits	Two 2-digit numbers

Primary 1 also introduces the concepts of addition and subtraction and the +, − and = symbols.

The same skills then appear inside other topics:

• Primary 2: adding and subtracting like fractions within one whole, with denominators not exceeding 12.
• Primary 3: adding and subtracting money in decimal notation.
• Primary 4: adding and subtracting decimals up to 2 decimal places.

In Primary 5 Foundation Mathematics, addition and subtraction algorithms up to 3 digits are revisited “without calculator”.

---

How Singapore Teaches Addition and Subtraction

1. Join and take away with objects

Children combine and separate small groups of real objects, then say what happened: “5 and 3 make 8.”

2. Think in parts and wholes

Number bonds show 8 as 5 and 3, or 6 and 2. Knowing the pairs that make 10 is especially useful.

3. Calculate mentally within 20

Students “make ten”: 8 + 5 = 8 + 2 + 3 = 13. The same idea works backwards for 13 − 5.

4. Line up the places for written methods

In the column method, ones go under ones and tens under tens. Students rename whenever a column needs it.

5. Check with the inverse

Every subtraction can be checked by addition, and every addition by subtraction.

6. Use models for word problems

A bar model shows which amount is the whole and which are the parts. The Singapore Math Bar Model guide explains the drawing method.

---

Worked Examples

This is Primary 3 work: algorithms up to 4 digits.

Adding two 2-digit numbers mentally is a Primary 3 skill.

---

Common Mistakes

• Subtracting the smaller digit from the larger. 52 − 27 becomes 35, because the child works out 7 − 2 in the ones. Fix: ask “Are there enough ones?” before every column.
• Misaligned columns. In 345 + 27, the 27 is written under the 34. Fix: line up the ones first, or use squared paper.
• Forgetting the renamed ten. 38 + 45 is given as 73 instead of 83. Fix: write the renamed ten clearly at the top of the next column.
• Renaming across zeros. In 5003 − 1467, the child cannot find a ten to rename. Fix: rename from the thousands, step by step, as in the worked example.
• Reading “more” as “add”. “Ali has 12 marbles. He has 5 more than Ben. How many does Ben have?” The answer is 7, not 17. Fix: draw a model to see which amount is larger.
• Using = as “the answer is”. 8 + 5 = 13 + 2 = 15 strings steps together incorrectly. Fix: both sides of = must have the same value, so write each step on a new line.

---

Teaching Addition and Subtraction Outside Singapore

• “Renaming”. Singapore materials say “renaming”, and the syllabus uses the phrase “without renaming”. You may know it as regrouping, carrying or borrowing.
• Number bonds. Number bonds are a common Singapore Math picture of part-whole thinking. They support mental calculation within 20.
• Timing. Singapore reaches 4-digit written methods in Primary 3. Your local curriculum may differ, so use the Singapore Math Grade Levels guide to judge readiness.
• Money. Singapore uses dollars and cents. In Primary 3, students add and subtract money in decimal notation, such as $4.85 + $2.30 = $7.15.
• Mental first. Mental calculation is listed at every level from Primary 1 to Primary 3. Do not drop it once the written method is learned.

---

How to Practise Addition and Subtraction at Home

1. Practise the pairs that make 10 until they are instant.
2. Do three mental questions a day, said aloud.
3. Do one written question with renaming, and check it with the inverse.
4. Make a subtraction question from every addition fact: if 47 + 38 = 85, what is 85 − 38?
5. Solve one word problem a day with a quick model.
6. Once a week, mix addition and subtraction so the child must choose.

Ten minutes a day is enough when it is regular.

---

Try These

1. Work out 6 + 8 + 4.
2. Work out 3000 − 1258.
3. Work out 64 − 29 mentally.
4. A library has 2365 books. It buys 1478 more. How many books does it have now?

Answers

1. 18. Add 6 + 4 = 10 first, then 10 + 8 = 18.
2. 1742. Check: 1742 + 1258 = 3000.
3. 35. Take away 30 to get 34, then add 1 back.
4. 3843. 2365 + 1478 = 3843. Check: 3843 − 1478 = 2365.

---

What Comes Next

• Multiplication Tables builds on repeated addition and equal groups.
• Money applies addition and subtraction to dollars and cents.
• Adding and Subtracting Fractions uses the same part-whole thinking with fractions.

Strong addition and subtraction make every later topic lighter.

---

Frequently Asked Questions

When do Singapore students learn addition and subtraction?

From Primary 1 to Primary 3 as a main topic. After that, the skills are used inside fractions, decimals and measurement.

How big are the numbers at each level?

Within 100 in Primary 1, up to 3 digits in Primary 2 and up to 4 digits in Primary 3.

What does “renaming” mean?

Changing 1 ten into 10 ones, or 10 ones into 1 ten, so that a column can be added or subtracted. Other curricula may call it regrouping, carrying or borrowing.

Should my child learn mental or written methods first?

Both are in the syllabus at every level. Mental work within 20 usually comes first, and written methods follow as the numbers grow.

Are number bonds part of the Singapore syllabus?

Number bonds are widely used in Singapore Math materials to show part-whole relationships. The syllabus itself lists the relationship between addition and subtraction.

Why does my child get subtraction wrong but addition right?

Renaming in subtraction is harder, especially across zeros. Practise checking each subtraction with addition.

---

Helpful Reading

• Singapore Mathematics | International Edition: Whole Numbers and Place Value
• Singapore Mathematics | International Edition: Multiplication Tables
• Singapore Mathematics | International Edition: Money
• Primary Mathematics: Mental Calculation, Number Bonds and Compensation | Worked Learning Guide
• Singapore Math Number Bonds | Part–Whole Thinking and Mental Mathematics
• Singapore Math Bar Model | A Guide to Model Drawing
• MOE Primary Mathematics Syllabus

---

Addition and Subtraction in Singapore Mathematics

Parts and wholes.

Make ten.

Line up the places.

Rename when a column needs it.

Check with the inverse.

These habits begin with small numbers in Primary 1.

By Primary 3 they carry 4-digit numbers, and after that they carry almost everything else.

---

Ask Bukit Timah Tutor

Bukit Timah Tutor teaches Mathematics in small groups of three students in Singapore.

If your child is learning Singapore Mathematics at home, in an international school or in a Singapore school, and you are unsure where to begin with this topic, send us a short message with the student’s level and one example of the work.

Bukit Timah Tutor
8 Fourth Avenue, Singapore 268674
Near Sixth Avenue MRT
Three-student Mathematics tutorials
By appointment

Properly taught kids shine a bright light into the future.

Singapore Mathematics | International Edition is a Bukit Timah Tutor guide series for families and teachers outside Singapore. It is not a textbook and is not affiliated with MOE, SEAB or any publisher. Syllabus details were checked against MOE and SEAB documents in October 2026. Always confirm current requirements with your school.

← Previous: Singapore Mathematics | International Edition: Whole Numbers and Place Value
Next: Singapore Mathematics | International Edition: Multiplication Tables →
All 100 topics in the International Edition