The idea, step by step
Every unit must match
An informal unit can be a clip, block or scoop. Choose units that are the same size. Different-sized blocks do not give a fair length count.
Start at one end. Place units end to end without gaps or overlaps. Count the units that reach the other end.
Keep the unit the same
A desk measured with small clips may use more clips than the same desk measured with large clips. The desk did not grow: the unit changed.
For mass, use equal counters on a balance. For capacity, fill the same scoop to the same level. Say the unit with the count: 6 blocks long or 4 cups full.
A common trap
Any six blocks make the same length.
Instead: The units must have equal size and be placed fairly.
See the thinking
A careful row
How long is the strip in equal tiles?
- Every tile has the same width.
- They touch with no gaps or overlaps.
- Count six tiles.
A gap is not a unit
Leo uses 4 blocks along a book but leaves gaps. Is the book exactly 4 blocks long?
- The gaps cover some length without being counted.
- Move the blocks together and measure again.
Check your understanding
A strip is covered by 5 equal clips, with no gaps. What is its length?
Show answer
5 clips long.
Each clip is one equal unit. Five clips cover the strip.
Your turn
6 questions · Work at your own pace.
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 ↗