Year 6 Maths Decimals

Round decimals - to 1 decimal place

20 practice questions 0 video lessons Theory + worked examples

Every question with a fully worked solution.

Theory

To round to one decimal place (the nearest tenth), look at the hundredths digit: \(5\) or more rounds the tenths up, \(4\) or less keeps it. This Year 6 maths page shows the rule on a number line and the special case when the tenths digit is \(9\).

One decimal place means one digit after the point. \(5.43\) to one decimal place is \(5.4\), because it is closer to \(5.4\) than to \(5.5\).

Only the hundredths digit decides; digits after it do not matter. \(12.349\) rounds to \(12.3\).

If the tenths digit is \(9\) and you round up, \(10\) tenths make \(1\) whole: \(3.95\) rounds to \(4.0\), and \(9.97\) rounds to \(10.0\).

Keep the zero: \(4.0\) shows the answer is correct to one decimal place.

\(2.67\) is past \(2.65\), so it rounds up to \(2.7\).

\(3.95\) is halfway, so it rounds up to \(4.0\).

The rule:

\[ \text{hundredths } 0\text{-}4 \Rightarrow \text{keep the tenths} \]

hundredths 0 to 4 keep the tenths

\[ \text{hundredths } 5\text{-}9 \Rightarrow \text{add 1 tenth} \]

hundredths 5 to 9 add one tenth

\[ 0.9 + 0.1 = 1.0 \]

0.9 + 0.1 = 1.0

One digit decides. For \(12.349\), the hundredths digit is \(4\): \(12.3\).

Keep the zero. Write \(4.0\), not \(4\), when rounding to one decimal place.

Rounding to one decimal place

Underline the tenths digit.
Look at the hundredths digit.
5 or more: add \(1\) to the tenths digit (carry if it was \(9\)). 4 or less: keep it.
Write the answer with exactly one digit after the point.

Example 1 — Round down

Round \(5.43\) to one decimal place.

Solution

Hundredths digit \(3\): \(5.4\).

Example 2 — Round up

Round \(2.67\) to one decimal place.

Solution

Hundredths digit \(7\): \(2.7\).

Example 3 — Halfway

Round \(7.65\) to one decimal place.

Solution

Hundredths digit \(5\): round up to \(7.7\).

Example 4 — Carry

Round each to one decimal place.
(i) \(3.95\)
(ii) \(9.97\)

Solution

(i) \(4.0\)
(ii) \(10.0\)

Example 5 — Ignore later digits

Round \(12.349\) to one decimal place.

Solution

Hundredths digit \(4\): \(12.3\). The \(9\) does not matter.

Example 6 — Small numbers

Round \(0.08\) to one decimal place.

Solution

Tenths digit \(0\), hundredths \(8\): round up to \(0.1\).

Example 7 — Measurement

A leaf is \(6.43\) cm long.
(i) Round it to one decimal place.
(ii) Which digit did you look at?

Solution

(i) \(6.4\) cm
(ii) The hundredths digit, \(3\)

Example 8 — Find the mistake

Zac rounded \(3.95\) to \(3.10\). What is right?

Solution

Ten tenths make one whole, so \(3.9\) plus one tenth is \(4.0\).

Common pitfalls

Not carrying. \(3.95\) is \(4.0\), not \(3.10\).

Dropping the zero. Write \(4.0\) to show one decimal place.

Rounding from the last digit. \(12.349\): look at the \(4\), not the \(9\).

Changing the whole number. Unless you carry, the whole number stays the same.

Frequently asked questions

What does one decimal place mean?

One digit after the decimal point: tenths.

Which digit decides?

The hundredths digit.

What is 3.95 to one decimal place?

\(4.0\).

Why write 4.0 and not 4?

The zero shows the answer is given to one decimal place.

What is 0.08 to one decimal place?

\(0.1\).

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Round decimals - to 2 decimal places

Round decimals - to 1 decimal place

📖 Theory

Rounding to one decimal place

Common pitfalls

Frequently asked questions

Theory