See it
Hundred grid
Percent, fraction and decimal are one value.
1
Convert
0.25 = 25% = 1/4. 0.5 = 50% = 1/2.
2
Percentage of a Number
'20% of 80' means 20/100 × 80 = 16.
3
Percentage Change
(New − Old) / Old × 100%. Positive = increase, negative = decrease.
4
Discount & Interest
Final price = Original × (100 − discount%) / 100.
Common Mistakes
- Using the new value instead of old as the base
- Confusing % of vs % increase
- Adding percentages that share different bases
Teaching Team Tip
Write '100 units = original' at the top of the page. Everything follows.
Worked Example
Try it, then check the steps
Question
A $60 shirt is discounted by 25%. Final price?
Steps
- 1Discount = 25/100 × 60 = $15
- 2Final = 60 − 15 = $45
What to do next
Learn Percentage
Everything in the library for this topic