The strategy
How it works
Look for an addend close to 10, 20, or another multiple of 10.
Work out how much it needs to reach that friendly number.
Take that amount from the other addend, then add what remains.
See it in action
Worked examples
Example 18 + 7
- 8 needs 2 to make 10.
- Split 7 into 2 and 5.
- 10 + 5 = 15.
Answer: 15
Example 228 + 6
- 28 needs 2 to make 30.
- Split 6 into 2 and 4.
- 30 + 4 = 34.
Answer: 34
A quick heads-up
Common mistakes to avoid
- Taking more than the amount needed to reach ten; split the second number before moving anything.
- Making ten but forgetting to add the leftover part.
Your turn
Check your understanding
Choose an answer to see instant feedback and a short explanation. You can take the quiz again any time.
Question 1 of 3
What is 9 + 6 using make ten?
9 needs 1 to make 10. Move 1 from 6, leaving 5; 10 + 5 = 15.
How much does 27 need to reach 30?
27 + 3 = 30, so move 3 from the other addend.
What is 18 + 5?
18 needs 2 to make 20. Split 5 into 2 + 3, then 20 + 3 = 23.
Keep the momentum
Try a few practice problems
Choose a comfortable range and work through a short round with the free mental math trainer.