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Percentages
Per-cent literally means per-hundred. A percentage is a fraction with 100 on the bottom — written without showing the 100.
Percent of a whole
Slide it. Watch the bar and the answer change.
35%
35% of 80 is
28
(35/100) × 80
What does 35% mean?
35% is the same as 35/100 or 0.35. So 35% of 80 means: take 80, split it into 100 equal pieces, and grab 35 of them.
Three useful tricks
- 10% — divide by 10. (10% of 80 = 8.)
- 1% — divide by 100. (1% of 80 = 0.8.)
- 50% — divide by 2. Half.
Build it from 10%
To find 35% of 80: 10% is 8, so 30% is 24. Then 5% is half of 10%, which is 4. Add: 24 + 4 = 28.
Discounts
A jacket costs $60 with 25% off. The discount is 0.25 × 60 = 15. The new price is 60 − 15 = 45.
Going the other way
12 out of 50 students passed. What percentage? 12 / 50 = 0.24 = 24%.
Quick check
- What is 20% of 150?
- What percentage is 9 out of 30?
- A $40 game is 15% off. What's the new price?
Answers: 30, 30%, and $34.