Stage 2 · Add & subtract strategies
Adding 9 and 8
+9: add 10, take 1 back (+8: take 2).
How to do it
Method
+9: add 10, take 1 back (+8: take 2)
16 + 9 = 16 + 10 − 1 = 25
Another way
Column addition
Ones 6 + 9 = 15, write 5, carry 1; tens 1 + 1 = 2 → 25
In full
Add 9 by adding 10 and taking one back: 16 + 9 → 26 − 1 = 25. Add 8 by adding 10 and taking two: 16 + 8 → 26 − 2 = 24. This compensation trick scales to 19, 29, 98 and beyond. Adding in columns works too and gives the same answer, but compensation is quicker in your head.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
6 + 9
Show the answer and working
Answer: 6 + 9 = 15
Adding 9 is adding 10 and taking 1 back: 6 + 10 = 16, 16 − 1 = 15
Example 2
5 + 9
Show the answer and working
Answer: 5 + 9 = 14
Adding 9 is adding 10 and taking 1 back: 5 + 10 = 15, 15 − 1 = 14
Example 3
2 + 8
Show the answer and working
Answer: 2 + 8 = 10
Adding 8 is adding 10 and taking 2 back: 2 + 10 = 12, 12 − 2 = 10
Example 4
18 + 8
Show the answer and working
Answer: 18 + 8 = 26
Adding 8 is adding 10 and taking 2 back: 18 + 10 = 28, 28 − 2 = 26
Practise adding 9 and 8 in the game →Stage 2 · Add & subtract strategies · Free to start, unlimited questions, no download