Understand the idea.
Trade equal amounts
Regrouping trades equal amounts: one ten for ten ones, or one hundred for ten tens. Imagine opening a bundle rather than adding objects. There are more loose pieces afterwards, but their total value has not changed.
More than one name
One number can have several group names. In , trading the hundred gives twelve tens and six ones. Trading one of its original two tens instead gives one hundred, one ten and sixteen ones. Each collection still totals .
| Hundreds | Tens | Ones |
|---|---|---|
| 1 | 2 | 6 |
| 0 | 12 | 6 |
| 1 | 1 | 16 |
See the method in action.
Trade a hundred
Rename 240 using only tens.
Worked solution
- 1
Split the number into hundreds and tens.
There are two hundreds and four tens, with no ones.
- 2
Trade each hundred for ten tens.
Each hundred has the same value as ten tens.
- 3
Join all the tens.
The original four tens join the twenty renamed tens, so is twenty-four tens.
240 = 24 tens.
Trade for more ones
Rename 153 using 4 tens.
Worked solution
- 1
Show the usual grouping.
The number begins with one hundred, five tens and three ones.
- 2
Trade one of the five tens.
Trading a ten leaves four tens and releases ten ones.
- 3
Combine the loose ones.
The ten released ones join the three ones already there.
- 4
Check the renamed collection.
One hundred, four tens and thirteen ones preserve the original value.
1 hundred, 4 tens and 13 ones.
Try it yourself.
Check your understanding
Are 17 tens and 4 ones equal to 174?
Show answer & reasoning
Yes
Yes. Seventeen tens have a value of , and . More than nine tens can be used when describing a collection.
Keep practising
6 worksheet questions
Read the questions online
- Rename 60 as ones.
- Rename 300 using only tens.
- What number is 18 tens and 2 ones?
- Complete: .
- Are 2 hundreds and 15 tens equal to 350? Explain.
- Give two different groupings of 208.
Read the worked solutions
- Rename 60 as ones.
6 tens are equal to 60 ones.
60 ones. - Rename 300 using only tens.
Each hundred is 10 tens: .
30 tens. - What number is 18 tens and 2 ones?
.
182 - Complete: .
; 17 more makes 147.
17 - Are 2 hundreds and 15 tens equal to 350? Explain.
2 hundreds are 200 and 15 tens are 150; together they make 350.
Yes. - Give two different groupings of 208.
, so both groupings have value 208.
For example, 2 hundreds and 8 ones; or 20 tens and 8 ones.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Reading/ordering numbers; hundreds/tens/ones; zero; regrouping and renaming.
Official curriculum source ↗