Step-by-step Maths Level 3: Adding and subtracting within 1000

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.
   681 over 7
2. Exchange 1 ten for 10 ones. The ones on top (1) are fewer than the ones below (7), so we need more ones.
   8 tens become 7 tens, and the ones go from 1 to 11
3. Subtract the ones. 11 - 7 = 4.
   11 - 7 = 4
4. Subtract the tens. 7 - 0 = 7.
   7 - 0 = 7
5. Subtract the hundreds. 6 - 0 = 6.
   6 - 0 = 6
6. Write the answer. Read the columns from left to right.
   674

Check. Check: 674 + 7 = 681.

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

Method. Add the ones, then the tens, then the hundreds. Carry any ten or hundred you make.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   759 over 115
2. Add the ones. The ones make 10 or more, so write the ones digit and carry 1 ten.
   9 + 5 = 14, write 4 and carry 1
3. Add the tens. Add the carried ten with the tens.
   5 + 1 + 1 carried = 7
4. Add the hundreds. Add any carried hundred too.
   7 + 1 = 8
5. Write the answer. Read the columns from left to right.
   874

Check. Check: 874 - 115 = 759.

Watch out. When the ones make 10 or more, carry a ten to the tens column. Do not forget it.

Method. Add the ones, then the tens, then the hundreds. Carry any ten or hundred you make.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   852 over 48
2. Add the ones. The ones make 10 or more, so write the ones digit and carry 1 ten.
   2 + 8 = 10, write 0 and carry 1
3. Add the tens. Add the carried ten with the tens. The tens make 10 or more, so write the tens digit and carry 1 hundred.
   5 + 4 + 1 carried = 10
4. Add the hundreds. Add any carried hundred too.
   8 + 0 + 1 carried = 9
5. Write the answer. Read the columns from left to right.
   900

Check. Check: 900 - 48 = 852.

Watch out. When the tens make 10 or more, carry a hundred to the hundreds column.

Method. Add the ones, then the tens, then the hundreds. Carry any ten or hundred you make.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   39 over 18
2. Add the ones. The ones make 10 or more, so write the ones digit and carry 1 ten.
   9 + 8 = 17, write 7 and carry 1
3. Add the tens. Add the carried ten with the tens.
   3 + 1 + 1 carried = 5
4. Write the answer. Read the columns from left to right.
   57

Check. Check: 57 - 18 = 39.

Watch out. When the ones make 10 or more, carry a ten to the tens column. Do not forget it.

Method. Add the ones, then the tens, then the hundreds. Carry any ten or hundred you make.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   837 over 27
2. Add the ones. The ones make 10 or more, so write the ones digit and carry 1 ten.
   7 + 7 = 14, write 4 and carry 1
3. Add the tens. Add the carried ten with the tens.
   3 + 2 + 1 carried = 6
4. Add the hundreds. Add any carried hundred too.
   8 + 0 = 8
5. Write the answer. Read the columns from left to right.
   864

Check. Check: 864 - 27 = 837.

Watch out. When the ones make 10 or more, carry a ten to the tens column. Do not forget it.

Method. Find the operation, then work out the total.

1. Find the operation. We are putting two amounts together, so we add.
   63 + 177
2. Work out the total. Use column addition with the ones first.
   63 + 177 = 240
3. Write the answer. This is the total in the question.
   240

Check. Check: 240 - 177 = 63.

Watch out. Look for words like more, altogether and in all. These mean add.

Method. Add the ones, then the tens, then the hundreds. Carry any ten or hundred you make.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   27 over 91
2. Add the ones. The ones make less than 10, so no ten is carried.
   7 + 1 = 8
3. Add the tens. There is no carried ten to add. The tens make 10 or more, so write the tens digit and carry 1 hundred.
   2 + 9 = 11
4. Add the hundreds. Add any carried hundred too.
   0 + 0 + 1 carried = 1
5. Write the answer. Read the columns from left to right.
   118

Check. Check: 118 - 91 = 27.

Watch out. When the tens make 10 or more, carry a hundred to the hundreds column.

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.
   324 over 307
2. Exchange 1 ten for 10 ones. The ones on top (4) are fewer than the ones below (7), so we need more ones.
   2 tens become 1 tens, and the ones go from 4 to 14
3. Subtract the ones. 14 - 7 = 7.
   14 - 7 = 7
4. Subtract the tens. 1 - 0 = 1.
   1 - 0 = 1
5. Subtract the hundreds. 3 - 3 = 0.
   3 - 3 = 0
6. Write the answer. Read the columns from left to right.
   17

Check. Check: 17 + 307 = 324.

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.
   345 - 167
2. Work out the answer. Use column subtraction, and exchange if needed.
   345 - 167 = 178
3. Write the answer. This is the number left.
   178

Check. Check: 178 + 167 = 345.

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.
   825 over 549
2. Exchange 1 ten for 10 ones. The ones on top (5) are fewer than the ones below (9), so we need more ones.
   2 tens become 1 tens, and the ones go from 5 to 15
3. Exchange 1 hundred for 10 tens. The tens on top are fewer than the tens below (4 tens), so we need more tens.
   8 hundreds become 7 hundreds, and 1 tens become 11 tens
4. Subtract the ones. 15 - 9 = 6.
   15 - 9 = 6
5. Subtract the tens. 11 - 4 = 7.
   11 - 4 = 7
6. Subtract the hundreds. 7 - 5 = 2.
   7 - 5 = 2
7. Write the answer. Read the columns from left to right.
   276

Check. Check: 276 + 549 = 825.

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 the total.

1. Find the operation. We are putting two amounts together, so we add.
   395 + 48
2. Work out the total. Use column addition with the ones first.
   395 + 48 = 443
3. Write the answer. This is the total in the question.
   443

Check. Check: 443 - 48 = 395.

Watch out. Look for words like more, altogether and in all. These mean add.

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.
   458 over 9
2. Exchange 1 ten for 10 ones. The ones on top (8) are fewer than the ones below (9), so we need more ones.
   5 tens become 4 tens, and the ones go from 8 to 18
3. Subtract the ones. 18 - 9 = 9.
   18 - 9 = 9
4. Subtract the tens. 4 - 0 = 4.
   4 - 0 = 4
5. Subtract the hundreds. 4 - 0 = 4.
   4 - 0 = 4
6. Write the answer. Read the columns from left to right.
   449

Check. Check: 449 + 9 = 458.

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

Method. Add the ones, then the tens, then the hundreds. Carry any ten or hundred you make.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   589 over 9
2. Add the ones. The ones make 10 or more, so write the ones digit and carry 1 ten.
   9 + 9 = 18, write 8 and carry 1
3. Add the tens. Add the carried ten with the tens.
   8 + 0 + 1 carried = 9
4. Add the hundreds. Add any carried hundred too.
   5 + 0 = 5
5. Write the answer. Read the columns from left to right.
   598

Check. Check: 598 - 9 = 589.

Watch out. When the ones make 10 or more, carry a ten to the tens column. Do not forget it.

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

1. Find the operation. Words like left, gives and empty mean take away.
   127 - 87
2. Work out the answer. Use column subtraction, and exchange if needed.
   127 - 87 = 40
3. Write the answer. This is the number left.
   40

Check. Check: 40 + 87 = 127.

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

Method. Add the ones, then the tens, then the hundreds. Carry any ten or hundred you make.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   961 over 9
2. Add the ones. The ones make 10 or more, so write the ones digit and carry 1 ten.
   1 + 9 = 10, write 0 and carry 1
3. Add the tens. Add the carried ten with the tens.
   6 + 0 + 1 carried = 7
4. Add the hundreds. Add any carried hundred too.
   9 + 0 = 9
5. Write the answer. Read the columns from left to right.
   970

Check. Check: 970 - 9 = 961.

Watch out. When the ones make 10 or more, carry a ten to the tens column. Do not forget it.

Method. Add the ones, then the tens, then the hundreds. Carry any ten or hundred you make.

1. Write the numbers in columns. Keep the ones under the ones and the tens under the tens.
   24 over 79
2. Add the ones. The ones make 10 or more, so write the ones digit and carry 1 ten.
   4 + 9 = 13, write 3 and carry 1
3. Add the tens. Add the carried ten with the tens. The tens make 10 or more, so write the tens digit and carry 1 hundred.
   2 + 7 + 1 carried = 10
4. Add the hundreds. Add any carried hundred too.
   0 + 0 + 1 carried = 1
5. Write the answer. Read the columns from left to right.
   103

Check. Check: 103 - 79 = 24.

Watch out. When the tens make 10 or more, carry a hundred to the hundreds column.