Two-digit adding and taking away · Usually met around P1
Column addition and subtraction
Ones under ones; start from the ones.
How to do it
Method
Ones under ones; start from the ones
Ones 7 + 8 = 15, write 5, carry 1; tens 4 + 3 + 1 = 8 → 85
Another way
Check in your head
47 + 30 + 8 = 85
In full
To write a sum in columns, line ones up under ones and tens under tens, put the + or − on the left and draw a line underneath. Start from the ones: if they make 10 or more, write what is left over in the ones and a small 1 above the tens, a ten carried over; then add the tens together with that 1. Taking away without exchanging: ones from ones, tens from tens. You can also work it out in your head to check: 47 + 38 = 47 + 30 + 8 = 85.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Work out the column subtraction. What goes under the line?
Show the answer and working
Answer: 68
Ones 8 − 0 = 8, tens 7 − 1 = 6: 68.
Example 2
Work out the column sum. What goes under the line?
Show the answer and working
Answer: 78
Ones 1 + 7 = 8, tens 4 + 3 = 7: 78.
Example 3
The column subtraction in the picture is correct.
True or false?
Show the answer and working
Answer: True
Ones from ones, tens from tens: 79 − 18 = 61.
Practise it in the game →Two-digit adding and taking away · Free to start, unlimited questions, no download