Understand the idea.
Every unit must match
An informal unit is an object used for measuring, such as a tile or clip. Choose matching units. For length, start at one end and lay them end to end. Gaps miss some length; overlaps count some length twice.
Keep the unit the same
Always say the unit with the number. Six small clips and six large clips need not cover the same length. For mass, balance against equal counters. For capacity, use the same cup filled to the same level each time.
See the method in action.
A careful row
How long is the strip in equal tiles?
Worked solution
- 1
Check the row is a fair measure.
The tiles match, touch without gaps or overlaps, and cover the strip from end to end.
- 2
Count every tile once.
There are six equal units covering the whole strip.
- 3
Name the unit with the length.
The count measures length in tiles, rather than centimetres or another unit.
6 tiles long.
A gap is not a unit
Leo uses 4 blocks along a book but leaves gaps. Is the book exactly 4 blocks long?
Worked solution
- 1
Look for unmeasured spaces.
The gaps cover part of the book but are not included in the four-block count.
- 2
Measure again with touching blocks.
Only equal units placed end to end give a fair length count.
- 3
Reject the exact four-block claim.
The first arrangement includes extra gap lengths, so it does not show exactly four blocks.
No. Measure again without gaps.
Try it yourself.
Check your understanding
A strip is covered by 5 equal clips, with no gaps. What is its length?
Show answer & reasoning
5 clips long.
Five equal clips cover the whole strip without gaps. Each clip is one unit, so the strip is five clips long.
Keep practising
6 worksheet questions
Read the questions online
- A ribbon is covered exactly by 7 equal tiles. What is its length?
- A bucket takes 6 full cups to fill. Every cup is the same. What is its capacity in cups?
- A box balances with 8 equal counters. What is its mass in counters?
- Nina measures with one long clip and three short clips. Why is 4 clips not a fair length measure?
- Three tiles overlap while measuring a strip. Should you keep the count or measure again?
- How many equal blocks cover row A?
Read the worked solutions
- A ribbon is covered exactly by 7 equal tiles. What is its length?
Count seven equal tiles.
7 tiles long. - A bucket takes 6 full cups to fill. Every cup is the same. What is its capacity in cups?
Six equal full cups fill it.
6 cups. - A box balances with 8 equal counters. What is its mass in counters?
Eight equal counters balance the box.
8 counters. - Nina measures with one long clip and three short clips. Why is 4 clips not a fair length measure?
A fair count needs equal-sized units.
The clips have different sizes. - Three tiles overlap while measuring a strip. Should you keep the count or measure again?
Place the tiles end to end without overlapping.
Measure again. - How many equal blocks cover row A?
Count the five equal blocks.
5 blocks.
Curriculum reference & lesson scope
Australian Curriculum v9 / SA Curriculum 2026
Length, mass and capacity; uniform informal units; smaller units for accuracy; comparison.
Official curriculum source ↗