Unit conversions | Year 4 | Ascent Library

01 / LEARN

Understand the idea.

Use the correct groups

Time units use different-sized groups: $1 minute = 60 seconds$ , $1 hour = 60 minutes$ and $1 day = 24 hours$ . Choose the relationship connecting the units you need.

To express a duration in smaller units, count how many smaller units are in every larger unit. Three hours contain three groups of 60 minutes. Time conversions do not all use tens or hundreds.

Time relationships
Unit	Equal duration
1 minute	60 seconds
1 hour	60 minutes
1 day	24 hours

Keep the remainder

To change a number of minutes into hours and minutes, take out complete groups of 60. For 95 minutes, one group uses 60 and leaves $95 - 60 = 35$ . The duration is therefore 1 hour 35 minutes.

Keep the remainder smaller than the size of a full group: fewer than 60 minutes after the hours, or fewer than 60 seconds after the minutes. Check by converting the complete groups back and adding the remainder.

02 / WORKED EXAMPLES

See the method in action.

EXAMPLE 01

Three hours

How many minutes are in 3 hours?

Worked solution

1
Use the hour-to-minute relationship.
$1 hour = 60 minutes$
The answer needs minutes, so replace each hour with its 60-minute group.
2
Count three groups.
$3 \times 60 = 180 minutes$
Three hours contain three equal 60-minute groups.
3
Check by regrouping.
$180 \div 60 = 3 hours$
The minute total returns to the original three-hour duration.

Answer

180 minutes.

EXAMPLE 02

A mixed duration

Write 150 seconds using minutes and seconds.

Worked solution

1
Make complete minute groups.
$2 \times 60 = 120 seconds$
Two full minutes fit into 150 seconds; three would require 180 seconds.
2
Find the seconds left.
$150 - 120 = 30 seconds$
These seconds remain after the two full minute groups have been used.
3
Combine the groups and remainder.
$150 seconds = 2 minutes 30 seconds$
The remaining 30 seconds are less than a complete minute, so the grouping is finished.

Answer

2 minutes 30 seconds.

03 / YOUR TURN

Try it yourself.

Check your understanding

How many minutes are in 2 hours 15 minutes?

Show answer & reasoning

135 minutes.

Two hours contain $2 \times 60 = 120$ minutes. Include the extra 15 minutes: $120 + 15 = 135$ minutes.

Keep practising

6 worksheet questions · 7 marks

Open worksheet Worked solutions

Read the questions online

Convert 4 minutes to seconds.
1 mark
Convert 2 hours to minutes.
1 mark
Convert 1 hour 20 minutes to minutes.
1 mark
Write 125 minutes as hours and minutes.
1 mark
Convert 2 days to hours.
1 mark
Luca says 3 minutes 20 seconds is 320 seconds. Correct his answer.
2 marks

Read the worked solutions

Equivalent correct methods earn the corresponding marks. Include units where asked.

Convert 4 minutes to seconds.
1 mark
$4 \times 60 = 240$ .
240 seconds.
Convert 2 hours to minutes.
1 mark
$2 \times 60 = 120$ .
120 minutes.
Convert 1 hour 20 minutes to minutes.
1 mark
$60 + 20 = 80$ .
80 minutes.
Write 125 minutes as hours and minutes.
1 mark
120 minutes makes 2 hours, leaving 5 minutes.
2 hours 5 minutes.
Convert 2 days to hours.
1 mark
$2 \times 24 = 48$ .
48 hours.
Luca says 3 minutes 20 seconds is 320 seconds. Correct his answer.
2 marks
3 minutes is 180 seconds.
$180 + 20 = 200$ seconds; time units are not groups of 100.
200 seconds.

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Curriculum reference & lesson scope

Australian Curriculum v9 / SA Curriculum Mathematics 2026

am/pm; unit conversions; start/finish/elapsed time.

Official curriculum source ↗

In this lesson

Understand the idea.

Use the correct groups

Keep the remainder

See the method in action.

Three hours

Use the hour-to-minute relationship.

Count three groups.

Check by regrouping.

A mixed duration

Make complete minute groups.

Find the seconds left.

Combine the groups and remainder.

Try it yourself.

Check your understanding

Keep practising