Percentages express parts per hundred. Once you recognize the pattern, discounts and markups become much easier to estimate mentally.
Discounts and markups
A 30% off sale means you pay 70% of the original price. A 15% markup adds 15% to your cost.
Quick mental math
10% is easy: move the decimal one place left. Double it for 20%, halve it for 5%.
Common questions
- Is 50% off the same as half price?
- Yes — both mean you pay half the original amount.
- How do tips relate to percentages?
- A 20% tip on $40 is $8, calculated as 0.20 × 40.