Percentages
Jessica White
7 min read
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Study Guide Overview
This guide covers percentages, fractions, and decimals for the SAT. It explains percentage calculations, including finding percentages of quantities, discounts, taxes, and interest. It also covers percent increase and decrease, including successive changes. Finally, it details conversions between fractions, decimals, and percentages.
#AP SAT (Digital) Math: Percentages, Fractions, and Decimals - Your Ultimate Guide 🚀
Hey there, future SAT superstar! This guide is your go-to resource for acing those percentage, fraction, and decimal questions. Let's get you feeling confident and ready to rock the exam!
#1. The Power of Percentages
Percentages are all about parts of a whole, and they're super common on the SAT. Think of them as a way to express fractions with a denominator of 100. Let's break it down:
#1.1. Understanding the Basics
- What is a Percentage? It's a number out of 100, shown with the "%" symbol. So, 50% means 50 out of 100. * Key Idea: The "whole" is always 100%, and the "part" is some percentage of that whole.
Finding a Percentage of a Quantity:
- Convert the percentage to a decimal (divide by 100).
- Multiply the decimal by the quantity.
Example: What is 25% of 80? 25% = 0.25. 0.25 * 80 = 20.
The "Is over Of" Trick:
- Is/Of = %/100
- If you're asked, "What percent of 50 is 10?" think: 10/50 = x/100. Solve for x!
#1.2. Practical Applications
- Discounts: 30% off a
100 item means a30 discount (100 * 0.30 =30). - Sales Tax: 7% tax on a
50 purchase is3.50 (50 * 0.07 =3.50). - Interest: 4% interest on
2000 savings is80 (2000 * 0.04 =80). - Data Analysis: If 60 out of 200 students like pizza, that's 30% (60/200 * 100 = 30%).
Quick Tip: To find 10% of a number, just move the decimal one place to the left. Then, you can easily find 5%, 20%, etc.
#2. Percent Increase and Decrease
Understanding how to calculate changes is crucial for many SAT problems. Let's dive in!
#2.1. Calculating Pe...
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