Calculating a percent of a number
To calculate a percent of a number, convert the percent to a decimal by dividing by 100 (or moving the decimal point two places left), then multiply. For example, 8% of 300 = 0.08 x 300 = 24. This Grade 8 math skill from Yoshiwara Core Math Chapter 2 is one of the most practically useful math operations students will use throughout their lives, appearing in sales tax, discounts, tips, interest rates, statistics, and data analysis. Mastering percent calculations builds the numerical fluency needed for consumer math, finance, and quantitative reasoning.
Key Concepts
Property To calculate a percent of a number: 1. Change the percent to a decimal fraction. 2. Multiply the number by the decimal fraction. To change a percent to a decimal fraction, divide the percent by 100, or move the decimal point two places to the left.
Examples To find 8% of 300, convert 8% to a decimal by moving the decimal point two places left: $8\% = 0.08$. Then multiply: $0.08 \times 300 = 24$. A phone costs 850 dollars and sales tax is 7.5%. Convert 7.5% to a decimal: $0.075$. The tax is $0.075 \times 850 = 63.75$ dollars. Calculate 150% of 60. First, change 150% to a decimal: $1.50$. Then, multiply: $1.50 \times 60 = 90$.
Explanation To use a percent in a calculation, you must first convert it into a form your calculator understands, like a decimal. Moving the decimal point two places left is a quick shortcut for dividing by 100.
Common Questions
How do you calculate a percent of a number?
Step 1: Convert the percent to a decimal by moving the decimal point two places left (dividing by 100). Step 2: Multiply that decimal by the number. For example, 15% of 200 = 0.15 x 200 = 30.
What is 8% of 300?
Convert 8% to a decimal: 8 / 100 = 0.08. Multiply: 0.08 x 300 = 24. So 8% of 300 is 24.
How do you convert a percent to a decimal?
Divide the percent by 100, or equivalently, move the decimal point two places to the left. For example, 25% becomes 0.25, 7.5% becomes 0.075, and 150% becomes 1.50.
When do 8th graders learn to calculate percents?
Students study percent calculations in Grade 8 math as part of Chapter 2 of Yoshiwara Core Math, which covers numbers and variables including decimal and percent operations.
What is 7.5% sales tax on an $850 item?
Convert 7.5% to decimal: 0.075. Multiply: 0.075 x 850 = $63.75. The sales tax is $63.75, and the total cost would be $850 + $63.75 = $913.75.
What does it mean when a percent is greater than 100%?
A percent greater than 100% means more than the whole. 150% of 60 = 1.50 x 60 = 90, which is greater than 60. This occurs in contexts like percent increase, where something grows beyond its original size.