Percentages

Percentages are a way of expressing a number as a fraction of 100. The word "percent" means "per hundred," so when we talk about percentages, we are talking about a number out of 100.

Converting between percentages and decimals

To convert a percentage to a decimal, divide the percentage by 100. For example, to convert 25% to a decimal, you would divide 25 by 100 to get 0.25.

To convert a decimal to a percentage, multiply the decimal by 100. For example, to convert 0.75 to a percentage, you would multiply 0.75 by 100 to get 75%.

Finding the percentage of a number

To find a certain percentage of a number, you can multiply the number by the decimal equivalent of the percentage. For example, to find 20% of 150, you would multiply 150 by 0.20 to get 30.

Calculating percentage increase or decrease

To calculate the percentage increase or decrease between two numbers, you can use the following formula:

Percentage change = ((new number - original number) / original number) * 100

If the result is positive, it's a percentage increase. If it's negative, it's a percentage decrease.

Study Guide

Understand the concept of percentages as fractions of 100.
Practice converting between percentages and decimals.
Learn how to find the percentage of a number.
Practice calculating percentage increase or decrease using the formula.
Work on real-world problems involving percentages, such as discounts, taxes, and tips.

Remember to use the conversion formulas, practice with sample problems, and apply the concepts to real-life situations to master the topic of percentages.