Singapore Mathematics | International Edition: Decimals

Singapore Math decimals guide for families and teachers outside Singapore. What Primary 4 and Primary 5 students learn about decimals, how Singapore teaches them through place value, and how to practise them at home.

A decimal is a fraction written in place value.

Once a child sees that, decimal work becomes place value work.

In Singapore Mathematics, decimals are introduced in Primary 4. Students read and write decimals up to 3 decimal places, compare and round them, convert between decimals and fractions, and calculate with them in carefully limited cases.

In Primary 5 they multiply and divide decimals by 10, 100, 1000 and their multiples, and use decimals to convert measurements. Decimals then support percentage, measurement and almost every later topic.

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

• understand what Singapore expects at Primary 4 and Primary 5;
• teach decimals at home in a clear sequence;
• prepare a child who is moving into a Singapore school; or
• support a student using Singapore Math materials in another country.

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What Decimals Mean in Singapore Mathematics

A decimal extends the place value chart to the right of the ones.

The first place after the decimal point is tenths. The next is hundredths. The next is thousandths.

Each place is one tenth of the place to its left, just as each whole-number place is ten times the place to its right.

So 0.7 means 7 tenths, 0.07 means 7 hundredths and 0.007 means 7 thousandths.

A number such as 2.45 can be read in more than one way: 2 ones, 4 tenths and 5 hundredths, or 2 and 45 hundredths. Being able to switch between these readings is the heart of the topic.

Singapore children usually meet decimal notation before the topic itself. In Primary 2 they read and write money in decimal notation, so $4.35 is often the first decimal a child sees.

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Where Decimals Sit in the Singapore Syllabus

Decimals are introduced in Primary 4 and extended in Primary 5.

At Primary 4, students learn:

• decimals up to 3 decimal places (tenths, hundredths and thousandths);
• comparing and ordering decimals;
• converting decimals to fractions, and fractions to decimals when the denominator is a factor of 10 or 100;
• rounding to the nearest whole number, 1 decimal place or 2 decimal places;
• adding and subtracting decimals up to 2 decimal places;
• multiplying and dividing decimals (up to 2 decimal places) by a 1-digit whole number;
• dividing a whole number by a whole number, with the quotient as a decimal; and
• rounding answers to a specified degree of accuracy.

At Primary 5, students learn:

• multiplying and dividing decimals (up to 3 decimal places) by 10, 100, 1000 and their multiples, without a calculator; and
• converting measurements between smaller and larger units in decimal form: km and m, m and cm, kg and g, and ℓ and ml.

Primary 5 also includes expressing fractions as decimals, under fraction and division.

In the Standard content, every decimal multiplication and division listed uses a whole-number multiplier or divisor: a 1-digit whole number at Primary 4, and 10, 100, 1000 or their multiples at Primary 5.

Level	What students do with decimals
Primary 4	Up to 3 decimal places; compare, convert, round; add and subtract up to 2 decimal places; multiply and divide by a 1-digit whole number
Primary 5	Multiply and divide by 10, 100, 1000 and their multiples; measurement conversions in decimal form; fractions as decimals
Secondary 1	Approximation and estimation, including decimal places and significant figures

Decimals also appear in Foundation Mathematics, where they are revisited at Primary 5 and Primary 6.

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How Singapore Teaches Decimals

1. Cut one whole into tenths

Start with one whole split into 10 equal parts. Each part is one tenth, written 0.1. Ten tenths make one whole again.

2. Cut a tenth into hundredths

Split one tenth into 10 equal parts to get hundredths, then repeat for thousandths. A place value chart with columns for ones, tenths, hundredths and thousandths keeps this visible.

3. Compare place by place

Line up the decimal points and compare from the left. In 0.6 and 0.58, compare tenths first: 6 tenths is more than 5 tenths, so 0.6 is greater.

4. Convert between decimals and fractions

Read the place to write the fraction: 0.35 = 35/100 = 7/20. To go the other way, make the denominator 10 or 100: 3/4 = 75/100 = 0.75.

5. Calculate with the decimal points lined up

In column addition and subtraction, the decimal points sit in one straight line. For 2.35 × 4, students multiply as with whole numbers and use place value to place the point: 9.40, which is 9.4.

6. Multiply and divide by 10, 100 and 1000

At Primary 5, students see that multiplying by 10 makes each digit worth ten times as much, so every digit moves one place to the left. Dividing by 100 moves every digit two places to the right.

The order matters. A child who learns “move the point” before understanding place value often moves it the wrong way.

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Worked Examples

This is the Primary 4 skill of dividing a whole number by a whole number with a decimal quotient. Notice that the method is ordinary long division that continues past the ones.

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Common Mistakes

• Thinking a longer decimal is bigger. A child says 0.25 is greater than 0.3 because 25 is greater than 3. Fix: compare tenths first, or write 0.3 as 0.30 so both have the same number of places.
• Misaligning the digits. In 4.5 + 2.36, the digits are lined up on the right instead of at the point. Fix: line up the decimal points and write 4.5 as 4.50.
• Rounding in stages. Rounding 2.47 to the nearest whole number by going 2.47, then 2.5, then 3. Fix: look only at the digit immediately after the place you are rounding to. 2.47 rounds to 2.
• Moving digits the wrong way. A child writes 3.06 × 100 = 0.0306. Fix: estimate first. Multiplying by 100 makes the number larger.
• Converting fractions by guesswork. A child writes 1/4 = 0.4. Fix: make the denominator 100 first: 1/4 = 25/100 = 0.25.
• Losing a zero in measurement. 2 m 5 cm is written as 2.5 m. Fix: 5 cm is 5 hundredths of a metre, so the answer is 2.05 m.

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Teaching Decimals Outside Singapore

Decimal ideas are much the same everywhere. A few points are worth knowing when you use Singapore materials.

• The decimal point. Singapore writes the decimal point as a dot, as in 2.5. If your child has learnt a decimal comma, as in 2,5, point out the change early.
• Money and metric contexts. Singapore uses Singapore dollars and cents and metric units, so many decimal questions are about prices, metres, kilograms and litres.
• Timing. In Singapore’s current syllabus, decimals are introduced in Primary 4. Your local curriculum may place them differently, so decide by readiness rather than age. The Singapore Math Grade Levels guide explains why direct conversions are unreliable.
• Prerequisites. Decimals depend on place value, division with remainder and fractions with denominators of 10 and 100. If those are weak, repair them first.
• Working without a calculator. The Primary 5 content specifies multiplying and dividing by 10, 100 and 1000 without a calculator, and PSLE Paper 1 does not allow calculators.

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How to Practise Decimals at Home

A short, regular routine works better than one long weekend session.

1. Use money. Write three prices with dollars and cents and read each one aloud in two ways.
2. Measure something with a metre ruler and write the length in metres and in centimetres.
3. Put three decimals in order, including one with a different number of decimal places.
4. Convert two fractions with denominators that divide 10 or 100 into decimals.
5. Do one division that gives a decimal answer, and check it by multiplying.
6. Once a week, mix decimals with fractions so the child must choose the form that makes a question easier.

Ten to fifteen minutes is enough when the work is focused.

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Try These

1. Arrange in order, starting with the smallest: 0.6, 0.509, 0.56.
2. Write 3/4 as a decimal, and 0.35 as a fraction in its simplest form.
3. Round 6.047 to 2 decimal places.
4. Find 3.06 × 100 and 45 ÷ 1000.

Answers

1. 0.509, 0.56, 0.6. Compare tenths first: 5, 5 and 6. Then compare hundredths of the first two: 0 and 6.
2. 0.75 and 7/20. 3/4 = 75/100, and 35/100 simplifies by dividing both terms by 5.
3. 6.05. The thousandths digit is 7, so the hundredths digit rounds up from 4 to 5.
4. 306 and 0.045. Multiplying by 100 makes the number larger; dividing by 1000 makes it smaller.

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What Comes Next

Decimals feed directly into the next topics.

• In Primary 5, Percentage builds on hundredths: 0.35 is 35 hundredths, or 35%.
• Also in Primary 5, Length, Mass and Volume uses decimals to convert between units.
• In Secondary 1, Approximation and Significant Figures extends rounding to significant figures and estimation.

A student who reads decimals as place value usually handles these later topics with far fewer errors.

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Frequently Asked Questions

When do Singapore students learn decimals?

Decimals are introduced in Primary 4. In Primary 5, students multiply and divide decimals by 10, 100, 1000 and their multiples, and convert measurements in decimal form.

How many decimal places do Primary 4 students work with?

They read, compare and order decimals up to 3 decimal places. Addition and subtraction go up to 2 decimal places, and they multiply and divide decimals with up to 2 decimal places by a 1-digit whole number.

Do Singapore primary students multiply a decimal by a decimal?

In the Standard content, the decimal multiplication listed uses a whole-number multiplier: a 1-digit whole number at Primary 4, and 10, 100, 1000 or their multiples at Primary 5.

Can my child use a calculator for decimals?

Build mental and written methods first. The Primary 5 content specifies some decimal work without a calculator, and PSLE Paper 1 does not allow calculators. Paper 2 does.

Why does Singapore link decimals to money and measurement?

Children write money in decimal notation from Primary 2, and Primary 5 uses decimals to convert measurements. Familiar contexts make the place values meaningful.

Are decimals part of Foundation Mathematics?

Yes. Foundation Mathematics revisits decimals at Primary 5 and Primary 6, including rounding and dividing a whole number by a whole number with a decimal quotient.

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Helpful Reading

• Singapore Mathematics | International Edition: Whole Numbers and Place Value
• Singapore Mathematics | International Edition: Rounding and Estimation
• Singapore Mathematics | International Edition: Percentage
• Primary Mathematics: Decimals, Rounding and Four Operations | Worked Learning Guide
• Primary Mathematics: Fractions, Decimals and the Same Whole | Worked Learning Guide
• Fractions, Decimals and Percentages | Mathematics Knowledge Object
• MOE Primary Mathematics Syllabus
• SEAB PSLE Formats Examined in 2026

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Decimals in Singapore Mathematics

Tenths, then hundredths, then thousandths.

Line up the points.

Compare from the left.

Estimate before you move a digit.

Taught this way, decimals stop being a rule about dots.

They become one place value system that runs in both directions.

That habit carries a student from Primary 4 into percentage, measurement and beyond.

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Ask Bukit Timah Tutor

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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.

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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.

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