The strategy
How it works
Break the requested percentage into easy pieces.
Calculate each piece of the original amount.
Add the pieces and check that the result is a sensible fraction of the whole.
See it in action
Worked examples
Example 115% of 240
- 10% of 240 is 24.
- 5% is half of 10%: 12.
- 24 + 12 = 36.
Answer: 36
Example 212% of 350
- 10% of 350 is 35.
- 1% is 3.5, so 2% is 7.
- 35 + 7 = 42.
Answer: 42
A quick heads-up
Common mistakes to avoid
- Finding each rate from a different base; every piece must be a percentage of the same original amount.
- Adding the rate numbers without calculating the matching amounts.
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 15% of 100?
10% of 100 is 10 and 5% is 5; together that is 15.
What is 20% of 150?
20% is two lots of 10%; 10% of 150 is 15, so 20% is 30.
What is 11% of 200?
10% is 20 and 1% is 2; add them to get 22.
Keep the momentum
Try a few practice problems
Choose a comfortable range and work through a short round with the free mental math trainer.