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Purcell Math

Math Methods Grades 4-8

Understanding Percents: A Practical Guide

Introduction

In math, percents are everywhere—from calculating sales tax to figuring out discounts. But what does a percentage actually mean, and how can we use it to make calculations easier? Today, we’re diving into the basics of percents and covering a few examples to show you how they work in real-life applications.

What Does “30 Percent” Mean?

A percent is simply a way to express a number as a part of 100. So, when we say “30 percent,” we’re really talking about the fraction 30/100, or 0.3. Here’s a practical look at how percents work in everyday math.

Example 1: Calculating a Percentage of a Number

Percentages are handy when calculating things like sales tax. Let’s walk through a quick example:

Problem: What is 15 percent of 20?
Solution: To find 15 percent of 20, multiply 20 by 0.15.

Step-by-Step Solution:
Step 1: Convert the percentage to a decimal by dividing by 100: 15% = 0.15
Step 2: Multiply 20 by 0.15: 0.15 × 20 = 3

So, 15 percent of 20 is 3.

Example 2: Finding Sales Tax

Let’s look at another practical scenario—finding the sales tax on a purchase.

Problem: How much sales tax would be paid on an item that costs 10 dollars if the tax rate is 15 percent?
Solution: Calculate 15 percent of 10 by multiplying 10 by 0.15.

Step-by-Step Solution:
Step 1: Convert 15 percent to a decimal: 0.15.
Step 2: Multiply 10 by 0.15: 0.15 × 10 = 1.50

So, you would pay $1.50 in sales tax on a $10 item.

Conclusion

Whether you’re figuring out sales tax or finding what part of a whole a number represents, percentages are essential for quick calculations. With practice, understanding and calculating percents becomes second nature, giving you a useful tool for everyday math.

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