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We can add numbers using the formal (efficient) written method
Year 4 Unit 11b
What we are learning:
- A written method is generally needed for the addition and subtraction of two-digit, three-digit and four-digit numbers as there may be several parts to each calculation. This can be too much to hold in our memory.
- The column method (where numbers are written in hundreds, tens and units columns) is referred to as a FORMAL written method or an EFFICIENT written method.
- Children will be introduced to the column method at the stage in their maths education when the teacher feels it is appropriate according to their ability to understand and use this method. Remember that progressing to a different method is not a race, and introducing your child to a concept that they are not ready for can knock confidence.
- This is an example of how to set out the formal written method for addition:
We always begin the addition sum in the units column. 9 plus 8 equals 17 which is too many for the units column. We exchange 10 units of these units for 1 ten which we carry into the tens column below the line, and put the 7 in the units column.
Now we add the tens. 7 add 6 add the 1 ten we have carried makes 14 tens (140). We exchange 10 tens for 100 which we carry underneath the line into the hundreds column, and put the 4 in the tens column.
Finally we add the hundreds. 4 plus 2 plus the 1 we have carried makes 7 (700). The answer is 747.
Activities you can do at home:
Try the calculations on the Activity Sheet together and talk about the method and the answers. Ask your child to explain what they are doing at each stage of the calculation for some sums. This will ensure they are developing the concepts securely.
Look for opportunities in real life to create additions like this. For example, make up a sum about the number of people at a sports match or a pop concert.
Good questions to ask:
What does this digit represent / stand for? (point at a single digit anywhere in the sum)
Why do you think we put the carrying numbers underneath the sum? (simply so they don’t get mixed up with the numbers!)
If your child:
Can do the calculation but cannot explain what they are doing.
Let them practice the method first until they are confident with it. Then go back over some of the sums they have already got right and explore them together, explaining each step. This is a different skill and needs practice.
Don’t rush this. Being able to explain your thinking is a vital skill to make sure we understand the concepts and can apply them in other situations.