Writing decimals

Home learning focus

Learn how to write decimals using place value columns.

This lesson includes:

  • one learning summary
  • four interactive activities

Learn

Decimals in daily life

Decimals are all around you:

  • They are used to write amounts of money (£1.99).
  • You see them when baking or on packets of food to show weight (1.5 kg of flour).
  • They’re used in length (1.45 km).
  • Even time uses decimals (10.15 seconds).

That is why it is important to understand how to write decimals and understand their place value.

Tenths and hundredths

We use a decimal point to separate the whole from the parts of a whole.

  • When one whole is divided into 10 parts, you call it a tenth.

  • When one whole is divided into 100 parts, you call it a hundredth.

You often see tenths and hundredths written as fractions, for example ⁹¹/₁₀₀.

Have a look at last week's lessons on tenths and hundredths for a reminder.

The place value columns for tenths and hundredths look like this:

Let's look at how you write decimals.

Example 1

How would you write thirteen and fifty-two hundredths as a decimal?

Use your knowledge of place value and partitioning. Thirteen is made up of one ten and three ones.

There are fifty-two hundredths. This is made up of 5 tenths and 2 hundredths. These numbers go after the decimal point.

So thirteen and fifty-two hundredths is written 13.52

Example 2

Write ²¹/₁₀₀ as a decimal.

Use your knowledge of place value: ²¹/₁₀₀ (21 hundredths) is made up of 2 tenths and 1 hundredth.

In a place value chart that would look like this:

There are no ones, so you write zero in the ones column to show this!

If you have no ones at all, you must write a zero before the decimal point. This is to show that it is a number smaller than one.

Practise

Activity 1

Rearrange the numbers into the correct place value columns.

Activity 2

Writing decimals

Answer the questions on the worksheet below from Twinkl - can you get them all right?

Writing decimals worksheet

Click here for the answer sheet

Activity 3

Decimals and measurement

Look at the worksheet below from Whizz Education. Write down your answers to the questions about decimals in measurement.

Remember, 1 cm = 10 mm

Decimals and measurement

Check here for the answer sheet

Activity 4

Guardians: Defenders of Mathematicia

Play the Palace of Place Value level in Guardians: Defenders of Mathematicia to test your knowlege of decimals and place value.

Guardians: Defenders of Mathematica

There's more to learn

Have a look at these other resources around the BBC and the web.

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