Algebra 1 / Unit 2: Solving Equations
2.6 Percents and Percent Change
Notes
- Percent means "per hundred": $35\% = 0.35$.
- Percent of a number: $20\%$ of 80 is $0.20 \cdot 80 = 16$.
- Percent change $\displaystyle = \frac{\text{new} - \text{original}}{\text{original}} \times 100\%$. Positive means increase, negative means decrease.
- A price after a $15\%$ discount is $85\%$ of the original: $0.85p$.
Practice
What is $40\%$ of 65?
$0.40 \cdot 65 = 26$.
A game's price rises from $40 to $50. The percent increase is:
$\displaystyle \frac{50 - 40}{40} = 0.25$.
A $60 jacket is $30\%$ off. The sale price is:
$0.70 \cdot 60 = 42$.
Ready for more? Take the Unit 2 test.