Addition and Subtraction
Addition and Subtraction
Addition and subtraction are basic mathematical operations that are often needed to answer questions in all kinds of topics. They are important skills that underpin a lot of questions that your child may be expected to answer in their exam. The most common and easy method for addition and subtraction is the column method which we will explore in more depth.
Addition Column Method
Example of adding using the column method:
Calculate
Start with the units column on the right and work your way along the columns to the left.
So a is placed underneath lining up with the units column.
Now add the numbers in the tens column.
This number is greater than so place the underneath and carry the . The will be added on in the addition of the next column.
The hundreds column is next.
Don’t forget the that has been carried over.
So the number written underneath the hundreds column is
The thousands column is done in the same way.
So,
Subtraction Column Method
Example of subtracting using the column method:
Calculate
Similar to addition using the column method, start with the units column.
So, is placed in the units column of the answer.
Then move left onto the tens column. The top number is less than the bottom number so we will need to “borrow” a from the number in the hundreds column. In this case, the in the hundreds column becomes a and the is given to the tens column to make .
Now we can continue as the top number is greater than the bottom number.
So, goes in the tens column.
For the hundreds column we now have a instead of a There isn’t a number in the hundreds column for the bottom number, so the calculation becomes:
So,
Example 1: Decimals
Calculate
The important thing for your child to remember when adding decimals is to correctly line up the decimal points. In this example there are a different number of decimal places after the decimal points, so it’s easy to get confused!
It is also helpful to add a decimal point to the answer line underneath the other decimal points so it’s not forgotten later on.
In this example only has number after the decimal point but has numbers after the decimal point. To ensure everything is lined up correctly a can be added to make which doesn’t change the value of the number but makes it easier to line up.
So,
Example 2: Addition and Subtraction
Harvey received some money for his birthday. He received from his auntie and from his grandma.
Harvey spent on a new jumper.
How much of his birthday money does Harvey have leftover?
[2 marks]
First, addition is needed to find the total amount of birthday money Harvey received.
Then use subtraction to work out how much money he has left after buying the jumper.
Addition and Subtraction Example Questions
Question 1: Calculate
[1 mark]
The units and the tens columns can be subtracted without problem. The hundreds column “borrows” a from the thousands column.
The number in the thousands column becomes a and can be subtracted as normal.
Question 2: Maureen went to the bakery and bought some cakes for her tea party. She bought lemon drizzle cakes and chocolate cake.
How much did she spend in total at the bakery?
[1 mark]
Lemon drizzle cake costs and chocolate cake costs
Add these values using column method.
Remember to include twice as Maureen is buying lemon drizzle cakes!
So,
Question 3: Martin has .
He buys a jumper for and sells a scarf he owns for .
How much money does he now have?
This question combines addition and subtraction.
The full calculation is:
It is easier to split the question up into two steps, one for the subtraction and one for the addition.
Step 1:
Step 2:
Martin now has