Step-by-step Maths Level 3 Subtracting within 1000: check-up and practice test questions

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   21 over 12
2. Exchange 1 ten for 10 ones. The ones on top (1) are fewer than the ones below (2), so we need more ones.
   2 tens become 1 tens, and the ones go from 1 to 11
3. Subtract the ones. 11 - 2 = 9.
   11 - 2 = 9
4. Subtract the tens. 1 - 1 = 0.
   1 - 1 = 0
5. Write the answer. Read the columns from left to right.
   9

Check. Check: 9 + 12 = 21.

Watch out. Exchange a ten for ten ones when the ones on top are too small. Then take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   81 over 16
2. Exchange 1 ten for 10 ones. The ones on top (1) are fewer than the ones below (6), so we need more ones.
   8 tens become 7 tens, and the ones go from 1 to 11
3. Subtract the ones. 11 - 6 = 5.
   11 - 6 = 5
4. Subtract the tens. 7 - 1 = 6.
   7 - 1 = 6
5. Write the answer. Read the columns from left to right.
   65

Check. Check: 65 + 16 = 81.

Watch out. Exchange a ten for ten ones when the ones on top are too small. Then take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   224 over 8
2. Exchange 1 ten for 10 ones. The ones on top (4) are fewer than the ones below (8), so we need more ones.
   2 tens become 1 tens, and the ones go from 4 to 14
3. Subtract the ones. 14 - 8 = 6.
   14 - 8 = 6
4. Subtract the tens. 1 - 0 = 1.
   1 - 0 = 1
5. Subtract the hundreds. 2 - 0 = 2.
   2 - 0 = 2
6. Write the answer. Read the columns from left to right.
   216

Check. Check: 216 + 8 = 224.

Watch out. Exchange a ten for ten ones when the ones on top are too small. Then take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   716 over 141
2. Exchange 1 hundred for 10 tens. The tens on top are fewer than the tens below (4 tens), so we need more tens.
   7 hundreds become 6 hundreds, and 1 tens become 11 tens
3. Subtract the ones. 6 - 1 = 5.
   6 - 1 = 5
4. Subtract the tens. 11 - 4 = 7.
   11 - 4 = 7
5. Subtract the hundreds. 6 - 1 = 5.
   6 - 1 = 5
6. Write the answer. Read the columns from left to right.
   575

Check. Check: 575 + 141 = 716.

Watch out. When a column is too small, exchange one from the column to its left. Ten ones make one ten, ten tens make one hundred.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   696 over 9
2. Exchange 1 ten for 10 ones. The ones on top (6) are fewer than the ones below (9), so we need more ones.
   9 tens become 8 tens, and the ones go from 6 to 16
3. Subtract the ones. 16 - 9 = 7.
   16 - 9 = 7
4. Subtract the tens. 8 - 0 = 8.
   8 - 0 = 8
5. Subtract the hundreds. 6 - 0 = 6.
   6 - 0 = 6
6. Write the answer. Read the columns from left to right.
   687

Check. Check: 687 + 9 = 696.

Watch out. Exchange a ten for ten ones when the ones on top are too small. Then take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   905 over 767
2. Exchange 1 hundred for 10 tens. There are no tens to take from, so we first change a hundred into tens.
   9 hundreds and 0 tens become 8 hundreds and 10 tens
3. Exchange 1 ten for 10 ones. The ones on top (5) are fewer than the ones below (7), so we need more ones.
   10 tens become 9 tens, and the ones go from 5 to 15
4. Subtract the ones. 15 - 7 = 8.
   15 - 7 = 8
5. Subtract the tens. 9 - 6 = 3.
   9 - 6 = 3
6. Subtract the hundreds. 8 - 7 = 1.
   8 - 7 = 1
7. Write the answer. Read the columns from left to right.
   138

Check. Check: 138 + 767 = 905.

Watch out. When a column is too small, exchange one from the column to its left. Ten ones make one ten, ten tens make one hundred.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   670 over 223
2. Exchange 1 ten for 10 ones. The ones on top (0) are fewer than the ones below (3), so we need more ones.
   7 tens become 6 tens, and the ones go from 0 to 10
3. Subtract the ones. 10 - 3 = 7.
   10 - 3 = 7
4. Subtract the tens. 6 - 2 = 4.
   6 - 2 = 4
5. Subtract the hundreds. 6 - 2 = 4.
   6 - 2 = 4
6. Write the answer. Read the columns from left to right.
   447

Check. Check: 447 + 223 = 670.

Watch out. Exchange a ten for ten ones when the ones on top are too small. Then take away.

Method. Find the operation, then work out what is left.

1. Find the operation. Words like left, gives and empty mean take away.
   244 - 237
2. Work out the answer. Use column subtraction, and exchange if needed.
   244 - 237 = 7
3. Write the answer. This is the number left.
   7

Check. Check: 7 + 237 = 244.

Watch out. Words like left, gone and gives away mean take away.

Method. Find the operation, then work out what is left.

1. Find the operation. Words like left, gives and empty mean take away.
   949 - 492
2. Work out the answer. Use column subtraction, and exchange if needed.
   949 - 492 = 457
3. Write the answer. This is the number left.
   457

Check. Check: 457 + 492 = 949.

Watch out. Words like left, gone and gives away mean take away.

Method. Find the operation, then work out what is left.

1. Find the operation. Words like left, gives and empty mean take away.
   597 - 58
2. Work out the answer. Use column subtraction, and exchange if needed.
   597 - 58 = 539
3. Write the answer. This is the number left.
   539

Check. Check: 539 + 58 = 597.

Watch out. Words like left, gone and gives away mean take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   438 over 299
2. Exchange 1 ten for 10 ones. The ones on top (8) are fewer than the ones below (9), so we need more ones.
   3 tens become 2 tens, and the ones go from 8 to 18
3. Exchange 1 hundred for 10 tens. The tens on top are fewer than the tens below (9 tens), so we need more tens.
   4 hundreds become 3 hundreds, and 2 tens become 12 tens
4. Subtract the ones. 18 - 9 = 9.
   18 - 9 = 9
5. Subtract the tens. 12 - 9 = 3.
   12 - 9 = 3
6. Subtract the hundreds. 3 - 2 = 1.
   3 - 2 = 1
7. Write the answer. Read the columns from left to right.
   139

Check. Check: 139 + 299 = 438.

Watch out. When a column is too small, exchange one from the column to its left. Ten ones make one ten, ten tens make one hundred.

Method. Find the operation, then work out what is left.

1. Find the operation. Words like left, gives and empty mean take away.
   425 - 256
2. Work out the answer. Use column subtraction, and exchange if needed.
   425 - 256 = 169
3. Write the answer. This is the number left.
   169

Check. Check: 169 + 256 = 425.

Watch out. Words like left, gone and gives away mean take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   985 over 6
2. Exchange 1 ten for 10 ones. The ones on top (5) are fewer than the ones below (6), so we need more ones.
   8 tens become 7 tens, and the ones go from 5 to 15
3. Subtract the ones. 15 - 6 = 9.
   15 - 6 = 9
4. Subtract the tens. 7 - 0 = 7.
   7 - 0 = 7
5. Subtract the hundreds. 9 - 0 = 9.
   9 - 0 = 9
6. Write the answer. Read the columns from left to right.
   979

Check. Check: 979 + 6 = 985.

Watch out. Exchange a ten for ten ones when the ones on top are too small. Then take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   840 over 3
2. Exchange 1 ten for 10 ones. The ones on top (0) are fewer than the ones below (3), so we need more ones.
   4 tens become 3 tens, and the ones go from 0 to 10
3. Subtract the ones. 10 - 3 = 7.
   10 - 3 = 7
4. Subtract the tens. 3 - 0 = 3.
   3 - 0 = 3
5. Subtract the hundreds. 8 - 0 = 8.
   8 - 0 = 8
6. Write the answer. Read the columns from left to right.
   837

Check. Check: 837 + 3 = 840.

Watch out. Exchange a ten for ten ones when the ones on top are too small. Then take away.

Method. Find the operation, then work out what is left.

1. Find the operation. Words like left, gives and empty mean take away.
   883 - 666
2. Work out the answer. Use column subtraction, and exchange if needed.
   883 - 666 = 217
3. Write the answer. This is the number left.
   217

Check. Check: 217 + 666 = 883.

Watch out. Words like left, gone and gives away mean take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   602 over 583
2. Exchange 1 hundred for 10 tens. There are no tens to take from, so we first change a hundred into tens.
   6 hundreds and 0 tens become 5 hundreds and 10 tens
3. Exchange 1 ten for 10 ones. The ones on top (2) are fewer than the ones below (3), so we need more ones.
   10 tens become 9 tens, and the ones go from 2 to 12
4. Subtract the ones. 12 - 3 = 9.
   12 - 3 = 9
5. Subtract the tens. 9 - 8 = 1.
   9 - 8 = 1
6. Subtract the hundreds. 5 - 5 = 0.
   5 - 5 = 0
7. Write the answer. Read the columns from left to right.
   19

Check. Check: 19 + 583 = 602.

Watch out. When a column is too small, exchange one from the column to its left. Ten ones make one ten, ten tens make one hundred.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   615 over 7
2. Exchange 1 ten for 10 ones. The ones on top (5) are fewer than the ones below (7), so we need more ones.
   1 tens become 0 tens, and the ones go from 5 to 15
3. Subtract the ones. 15 - 7 = 8.
   15 - 7 = 8
4. Subtract the tens. 0 - 0 = 0.
   0 - 0 = 0
5. Subtract the hundreds. 6 - 0 = 6.
   6 - 0 = 6
6. Write the answer. Read the columns from left to right.
   608

Check. Check: 608 + 7 = 615.

Watch out. Exchange a ten for ten ones when the ones on top are too small. Then take away.

Method. Find the operation, then work out what is left.

1. Find the operation. Words like left, gives and empty mean take away.
   536 - 155
2. Work out the answer. Use column subtraction, and exchange if needed.
   536 - 155 = 381
3. Write the answer. This is the number left.
   381

Check. Check: 381 + 155 = 536.

Watch out. Words like left, gone and gives away mean take away.

Method. Find the operation, then work out what is left.

1. Find the operation. Words like left, gives and empty mean take away.
   966 - 92
2. Work out the answer. Use column subtraction, and exchange if needed.
   966 - 92 = 874
3. Write the answer. This is the number left.
   874

Check. Check: 874 + 92 = 966.

Watch out. Words like left, gone and gives away mean take away.

Method. Subtract the ones first. If the top digit is too small, exchange from the next column, then subtract.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   501 over 7
2. Exchange 1 hundred for 10 tens. There are no tens to take from, so we first change a hundred into tens.
   5 hundreds and 0 tens become 4 hundreds and 10 tens
3. Exchange 1 ten for 10 ones. The ones on top (1) are fewer than the ones below (7), so we need more ones.
   10 tens become 9 tens, and the ones go from 1 to 11
4. Subtract the ones. 11 - 7 = 4.
   11 - 7 = 4
5. Subtract the tens. 9 - 0 = 9.
   9 - 0 = 9
6. Subtract the hundreds. 4 - 0 = 4.
   4 - 0 = 4
7. Write the answer. Read the columns from left to right.
   494

Check. Check: 494 + 7 = 501.

Watch out. When a column is too small, exchange one from the column to its left. Ten ones make one ten, ten tens make one hundred.