The strategy
How it works
Find 10% by dividing the amount by 10.
Find 5% by halving 10%, or 1% by dividing by 100.
Combine or repeat these amounts to get the requested percentage.
See it in action
Worked examples
Example 110% of 80
- Divide by 10.
- 80 ÷ 10 = 8.
- So 10% of 80 is 8.
Answer: 8
Example 25% of 60
- 10% of 60 is 6.
- Half of 6 is 3.
- So 5% of 60 is 3.
Answer: 3
A quick heads-up
Common mistakes to avoid
- Dividing by 10 to find 1%; 1% means divide by 100.
- Treating 5% as half the whole amount; it is half of the 10% amount.
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 10% of 90?
Ten percent is one tenth: 90 ÷ 10 = 9.
What is 5% of 40?
10% of 40 is 4; half of 4 is 2.
What is 1% of 300?
Divide by 100: 300 ÷ 100 = 3.
Keep the momentum
Try a few practice problems
Choose a comfortable range and work through a short round with the free mental math trainer.