Unit 3: Subtraction

# Topic C: Renaming

When you subtract, you may need to rename. Renaming means changing from one place value to another.

For example:

• 1 ten can be renamed as 10 ones
• 1 hundred can be renamed as 10 tens
• 1  thousand can be renamed as 10 hundreds.

Renaming is an important part of subtracting. Sometimes the digit on top is smaller than the digit you are subtracting. This means that you will have to rename before you can subtract. This is also called borrowing.

Example A: 293

2 hundreds, 9 tens, 3 ones

renamed 2 hundreds, 8 tens, 13 ones

You borrow 1 ten. The 1 ten is renamed as 10 ones.

10 ones + 3 ones = 13 ones

Example B: 3782

3 thousands, 7 hundreds, 8 tens, 2 ones

Renamed 3 thousands, 6 hundreds, 18 tens, 2 ones

You borrow 1 hundred. The 1 hundred is renamed as 10 tens.

10 tens + 8 tens = 18 tens

Exercise One

Borrow from the number in the shaded box. Check your work using the answer key at the end of the exercise.

1. ten thousands thousands hundreds tens ones
423 4 2 3
4 1 13
2. ten thousands thousands hundreds tens ones
642
3. ten thousands thousands hundreds tens ones
1456
4. ten thousands thousands hundreds tens ones
5423
5. ten thousands thousands hundreds tens ones
6384

1. ten thousands thousands hundreds tens ones
642 6 4 2
6 3 12
2. ten thousands thousands hundreds tens ones
1456 1 4 5 6
1 4 4 16
3. ten thousands thousands hundreds tens ones
5423 5 4 2 3
5 4 1 13
4. ten thousands thousands hundreds tens ones
6384 6 3 8 4
6 2 18 4

Sometimes there is a zero in the place where you want to borrow from. You will need to move one more place value to the left and borrow from there.

Example C: 203

2 hundreds, 0 tens, 3 ones

renamed 1 hundreds, 10 tens, 3 ones

You borrow 1 hundred. The 1 hundred is renamed as 10 tens.

1 hundred, 9 tens, 13 ones

Then, you borrow 1 ten. The 1 ten is renamed as 10 ones.

10 ones + 3 ones = 13 ones

Example D: 30 782

3 ten thousands, 0 thousands, 7 hundreds, 8 tens, 2 ones

renamed 2 ten thousands, 10 thousands, 7 hundreds, 8 tens,

2 ones

You borrow 1 ten thousand. The 1 ten thousand is renamed as 10 thousands.

2 ten thousands, 9 thousands, 17 hundreds, 8 tens, 2 ones Then, you borrow 1 thousand. The 1 thousand is renamed as 10 hundreds.

10 hundreds + 7 hundreds = 17 hundreds

Exercise Two

Borrow from the number in the shaded box. Check your work using the answer key at the end of the exercise.

1. ten thousands thousands hundreds tens ones
403 4 0 3
3 10 3
3 9 13
2. ten thousands thousands hundreds tens ones
501
3. ten thousands thousands hundreds tens ones
904
4. ten thousands thousands hundreds tens ones
307

1. ten thousands thousands hundreds tens ones
403 4 0 3
3 10 3
3 9 13
2. ten thousands thousands hundreds tens ones
501 5 0 1
4 10 1
4 9 11
3. ten thousands thousands hundreds tens ones
904 9 0 4
8 10 4
8 9 14
4. ten thousands thousands hundreds tens ones
307 3 0 7
2 10 7
8 9 14

Need more practice?

Ask your instructor for some play money. Using the one, ten, hundred, thousand, ten thousand and hundred thousand dollar bills, practice trading one of one type of bill for ten of the lesser place value.

Example:

 ABE bucks \$10 Ten = ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One ABE bucks \$1 One

# Topic C: Self-Test

Mark     /12    Aim 10/12

1. Borrow from the number in the shaded box. (6 marks)
1. ten thousands thousands hundreds tens ones
783
2. ten thousands thousands hundreds tens ones
827
3. ten thousands thousands hundreds tens ones
7942
4. ten thousands thousands hundreds tens ones
5364
5. ten thousands thousands hundreds tens ones
28634
6. ten thousands thousands hundreds tens ones
62751
2. Borrow from the number in the shaded box. 6 marks.
1. ten thousands thousands hundreds tens ones
602
2. ten thousands thousands hundreds tens ones
805
3. ten thousands thousands hundreds tens ones
3075
4. ten thousands thousands hundreds tens ones
7048
5. ten thousands thousands hundreds tens ones
30478
6. ten thousands thousands hundreds tens ones
80946

## Answers to Topic C Self-Test

1. ten thousands thousands hundreds tens ones
783 7 8 3
7 7 13
2. ten thousands thousands hundreds tens ones
827 8 2 7
8 1 17
3. ten thousands thousands hundreds tens ones
7942 7 9 4 2
7 8 14 2
4. ten thousands thousands hundreds tens ones
5364 5 3 6 4
5 2 16 4
5. ten thousands thousands hundreds tens ones
28634 2 8 6 3 4
2 7 16 3 4
6. ten thousands thousands hundreds tens ones
62751 6 2 7 5 1
6 1 17 6 1
1. ten thousands thousands hundreds tens ones
602 6 0 2
5 10 2
5 9 12
2. ten thousands thousands hundreds tens ones
805 8 0 5
7 10 5
7 9 12
3. ten thousands thousands hundreds tens ones
3075 3 0 7 5
2 10 7 5
2 9 17 5
4. ten thousands thousands hundreds tens ones
7048 7 0 4 8
6 10 4 8
6 9 14 8
5. ten thousands thousands hundreds tens ones
30478 3 0 4 7 8
2 10 4 7 8
2 9 14 7 8
6. ten thousands thousands hundreds tens ones
80946 8 0 9 4 6
7 10 9 4 6
7 9 19 4 6