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Maths for SG Primary Schools

Primary 4 maths · Decimals · About 10 minutes

Use decimal place value to three decimal places

Predict, build a model, explain what changed, then use the relationship in a new situation.

Start the interactive lesson →Open practice activity

What you will learn

Models used: number sentences, stories, diagrams.

Before you start

Connect the action to the maths

One square is one whole. Four tenths of it is coloured. How is that different from four hundredths?

  1. The whole grid has 100 equal squares. One full row is 10 hundredths, or one tenth.

    This full square is one whole. A row is one tenth. Four complete rows cover four tenths.

    4/10 = 0.4

    One small square is one hundredth of the whole. Ten small squares make one tenth, so the same shaded amount can be described in more than one way.

    40/100 = 0.4 = 40%

  2. The whole grid has 100 equal squares. One full row is 10 hundredths, or one tenth.

    Each row contains ten small squares. One small square is one hundredth. Four small squares cover much less than four rows.

    4/100 = 0.04

    One small square is one hundredth of the whole. Ten small squares make one tenth, so the same shaded amount can be described in more than one way.

    4/100 = 0.04 = 4%

  3. Read the place heading before the digit. A counter in a different column has a different value.

    Imagine cutting each small square into ten equal pieces again. Four of those tiny pieces are four thousandths. The chart records their size with a different column.

    4/1000 = 0.004

    0.004 = 4 thousandths

  4. Read the place heading before the digit. A counter in a different column has a different value.

    Now put these three amounts together: four tenths, four hundredths and four thousandths. Each needs its own column because the units have different sizes.

    0.444 = 0.4 + 0.04 + 0.004

    0.444 = 4 tenths + 4 hundredths + 4 thousandths

Worked example: Read a number with an empty place

In 0.306, what is the value of the digit 6?

0.306 = 3 tenths + 6 thousandths

  1. Read the place heading before the digit. A counter in a different column has a different value.

    The three is in tenths. The zero holds the hundredths place, so the six belongs in thousandths.

    0.306 = 3 tenths + 6 thousandths

  2. Read the place heading before the digit. A counter in a different column has a different value.

    The question asks for the value, not the digit alone. Six copies of what size?

    In 0.306, what is the value of the digit 6?

    0.006

  3. Read the place heading before the digit. A counter in a different column has a different value.

    Six thousandths is 0.006. Without the middle zero, 0.36 would put the six in hundredths and change its value.

    0.306 = 0.3 + 0.006

    0.306 = 3 tenths + 6 thousandths

Common mistakes to discuss

Check your understanding

Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.

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