Finding a Percent of a Number
Grade 8 math lesson on finding a percent of a number by converting the percent to a decimal and multiplying. Students learn to calculate percentages in real-world contexts including discounts, taxes, tips, and interest.
Key Concepts
Property Forty percent of the 30 students rode the bus. To find the number of students, convert the percent to a fraction and find that fractional part of the total: $\frac{2}{5} \text{ of } 30 = 12$.
Examples Find 25% of 44: First, $25\% = \frac{1}{4}$. Then, $\frac{1}{4} \cdot 44 = 11$. A tablet that costs 500 dollars is 30% off. The discount is: $30\% = \frac{3}{10}$. So, $\frac{3}{10} \cdot 500 = 150$ dollars off. 60% of the 15 players scored. That means: $60\% = \frac{3}{5}$. So, $\frac{3}{5} \cdot 15 = 9$ players scored.
Explanation What does "20% of 50" even mean? It's just a math mission where 'of' is code for 'multiply.' Your first step is to convert the percent to its fraction disguise (20% becomes $\frac{1}{5}$). Then, you multiply that fraction by the number. You're simply calculating a specific slice of the whole number pie!
Common Questions
How do you find a percent of a number?
To find a percent of a number, convert the percent to a decimal by dividing by 100, then multiply by the number. For example, 30% of 80 = 0.30 x 80 = 24. Alternatively, write 30/100 x 80 = 24.
How do you calculate a discount using percents?
To calculate a discount, find the percent discount of the original price, then subtract. For example, 25% off : 25% of 60 = 0.25 x 60 = discount. Sale price = - = .
How do you calculate sales tax?
To calculate sales tax, find the tax percent of the original price and add it. For example, 8% tax on a item: 8% of 50 = 0.08 x 50 = tax. Total = + = .
What are common applications of finding percent of a number?
Finding percent of a number is used for sales discounts, tip calculations at restaurants, sales tax, interest on loans, grade calculations, and probability comparisons in everyday life.