Place value of decimals (tenths and hundredths)

Learning focus

Learn how to write decimals using place value columns.

This lesson includes:

  • one learning summary
  • one interactive activity
  • a quiz

Quiz

Try the quiz below to find out how well you understand place value and decimals.

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.

If you need a reminder, you can take a look at this lesson about tenths and hundredths.

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 \( \frac{21}{100}\) as a decimal.

Use your knowledge of place value. \( \frac{21}{100}\) (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 have to write zero in the ones column. This shows that it is a number smaller than one.

\( \frac{21}{100}\) as a decimal is 0.21

Practise

Activity 1

Rearrange the numbers into the correct place value columns.

Play

Play Guardians: Defenders of Mathematica to learn more and sharpen your skills on this topic.

Guardians: Defenders of Mathematica

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