Understand the idea.
A unit can be too big
If a book ends between the fourth and fifth large tile, four tiles do not cover its whole length. Record that it is between those lengths, or try smaller equal units. Smaller units can describe the leftover part more closely.
More units does not mean a longer object
Changing units does not change the object. If two small tiles match one large tile, replace each large tile with a pair. The same length needs twice as many small tiles. Keep the unit name so the bigger count is understood.
See the method in action.
Change the unit
A shelf is 4 large blocks long. Each large block equals 2 small blocks. How many small blocks cover it?
Worked solution
- 1
Replace each large block with a pair.
The question gives two small blocks for each large block.
- 2
Count four pairs.
The shelf has four large-block lengths, so it needs four pairs of small blocks.
- 3
State the length using small blocks.
Only the measuring unit changed; the shelf stayed the same length.
8 small blocks.
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.
Worked solution
- 1
Change the two large tiles into small tiles.
Each of the two large tiles has the length of two small tiles.
- 2
Include the remaining small tile.
The extra tile was already small, so add it once.
- 3
Use one unit for the whole answer.
All parts of the strip have now been counted in small tiles.
5 small tiles.
Try it yourself.
Check your understanding
One large tile equals 2 small tiles. How many small tiles match 5 large tiles?
Show answer & reasoning
10 small tiles.
Replace each of five large tiles with two small tiles: . Ten small tiles match the same length.
Keep practising
6 worksheet questions
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?
.
6 small blocks. - One large scoop holds 2 small scoops. How many small scoops fill 4 large scoops?
.
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.
.
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 ↗