The idea, step by step
A unit can be too big
A book might be longer than 4 large tiles but shorter than 5. Saying exactly 4 misses part of the book.
Try smaller equal tiles. They may fit the end more closely. Smaller units still need to be placed without gaps.
More units does not mean a longer object
When two small tiles fit into one large tile, the same strip needs twice as many small tiles.
A strip 3 large tiles long is 6 small tiles long. The number changes because the unit changes, not because the strip changes.
A common trap
The strip got longer because the count increased.
Instead: Smaller units give a larger count for the same strip. Name the unit.
See the thinking
Change the unit
A shelf is 4 large blocks long. Each large block equals 2 small blocks. How many small blocks cover it?
- Replace each large block with two small blocks.
- Count 2, 4, 6, 8.
Cover the last part
A strip is 2 large tiles and 1 small tile long. Each large tile equals 2 small tiles. Find its length in small tiles.
- Two large tiles make 4 small tiles.
- Add the last tile: 4 + 1 = 5.
Check your understanding
One large tile equals 2 small tiles. How many small tiles match 5 large tiles?
Show answer
10 small tiles.
Count 2, 4, 6, 8, 10.
Your turn
6 questions · Work at your own pace.
Read the questions online
- One large block equals 2 small blocks. How many small blocks match 3 large blocks?
- One large scoop holds 2 small scoops. How many small scoops fill 4 large scoops?
- One large tile equals 2 small tiles. A strip is 3 large tiles and 1 small tile long. Find its length in small tiles.
- One large tile equals 2 small tiles. How many large tiles match 8 small tiles?
- A book ends between the fourth and fifth large tile. Which may give a closer measure: smaller equal tiles or larger tiles?
- Sam records 4 large clips. Ali records 8 small clips for the same ribbon. Could both be right? Explain.
Read the worked solutions
- One large block equals 2 small blocks. How many small blocks match 3 large blocks?
2 + 2 + 2 = 6.
6 small blocks. - One large scoop holds 2 small scoops. How many small scoops fill 4 large scoops?
2 + 2 + 2 + 2 = 8.
8 small scoops. - One large tile equals 2 small tiles. A strip is 3 large tiles and 1 small tile long. Find its length in small tiles.
Three large tiles make 6 small tiles.
6 + 1 = 7.
7 small tiles. - One large tile equals 2 small tiles. How many large tiles match 8 small tiles?
Make four pairs.
4 large tiles. - A book ends between the fourth and fifth large tile. Which may give a closer measure: smaller equal tiles or larger tiles?
Smaller units can fit the last part more closely.
Smaller equal tiles. - Sam records 4 large clips. Ali records 8 small clips for the same ribbon. Could both be right? Explain.
Different-sized units can give different counts for one length.
Yes, if each large clip equals 2 small clips.
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 ↗