Key takeaways
You do not need exact answers for most everyday percentages. A few tricks get you within a percent or two faster than you can unlock a phone.
- x % of y equals y % of x.
- Build from 1 %, 10 % and 50 % blocks.
- Round first, then adjust.
Swap the numbers
8 % of 25 feels hard. 25 % of 8 is 2. They are the same thing, because x % of y = y % of x.
Building blocks
- 1 % of 480 is 4.8. So 3 % is 14.4.
- 10 % of 480 is 48. So 5 % is 24 and 15 % is 72.
- 50 % of 480 is 240. So 45 % is 240 − 24 = 216.
Round, then adjust
17 % of 198: call it 17 % of 200 = 34, then take off 17 % of 2 (about 0.3). Answer: 33.7. Exact: 33.66.
Practice
Try 12 % of 150, 35 % of 80 and 6 % of 1,250 before reaching for the calculator, then check.
Related questions
- What is 8 % of 25?
