- Adding 2-figure numbers that involve a carry figure
- Adding from right to left
- Adding left to right
Adding from Right to Left
The traditional way to add, say, 56 + 26 is to put the numbers under each other and add from right to left.
56 + 26 82 1
First, in the units: 6+6=12, so put down 2 and carry 1.
Then add the tens: 5+2=7, and adding the carried 1 you get 8.
So the answer is 82.
Adding from Left to Right
When an addition sum has a carry, like 56 + 26, you can add it in your head like this:
In 56 + 26 you get 7 tens or 70
Then in the units you have 6 + 6 = 12
And 70 + 12 = 82.
Left to Right Written Down
What if you want to write down the left to right method: for example, to show your ‘working out’ in an exam?
You write it like this:
56 + 26 = 712 = 82
Notice you write the 12 as 12 to show that the 1 in the 12 has to be carried to the left.
Similarly, 48 + 45 = 813 = 93.
The Preferred Method
Working from left to right has many advantages: it’s more natural, there’s less to remember, and there’s less chance of making mistakes. Therefore, in this course, we will favor the left to the right method.