3.13 Percent of a Number - old

Introduction

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

Math Basics  >  Unit 3 Ratios and Percent  >  Lesson 3.13 Percent of a Number

Video Lesson

Click play to watch the video and answer the questions for points!

Practice Activity

+ Video Transcript

In this lesson, we're going to learn how to find the percent of a number. What is 3% of 19? In math, whenever you see the word “of” that's a clue that we need to multiply. So to find 3% of 19, we'll need to multiply 3% times 19. The other thing to keep in mind is that whenever you're doing calculations with percent, you have to change the percent to a fraction or a decimal first. So if we want to convert the 3% to a fraction, our problem becomes three over 100 times 19. Or we could also convert the percent to a decimal. In that case, the problem becomes 300ths or 0.03 times 19. Now that we've converted to a fraction or a decimal, we can go ahead and calculate the answer. So based on the fraction, we would multiply the three times 19, which gives us 57, and bring over the denominator of 100. So the answer would be 57 over 100. Or if we based it off of being a decimal, 300ths times 19 would give us 57 hundredths or zero point 57. So we could write our final answer either way 57 over 100 or 57 hundredths. Now we'll look at a few examples that involve finding less than 100% of a number, exactly 100% and more than 100% of that number. And as we go through these examples, we'll see if we can find a pattern that can help us when we're working on other problems. So let's take a look at the one on the left. We want to find 5% of 40. We can write it as a decimal 0.05 and then multiply that by 40. In that case, our final answer is two. So notice that our final answer of two is less than the original number that we started with, which was 40. So whenever our percentage is less than 100, our final answer is going to be less than the number that we started with. Now let's see if we have exactly 100% of a number. So 100%, when we convert it to either a fraction or a decimal, is just the whole number one. And so if we multiply one times 40, we end up with 40. So in this case, our answer is equal to the original number that we started with. So 100% of 40 will just be equal to 40. And let's see what happens when we have more than 100% of a number. So in the last example, we have 105% of 40. If we convert 105% to a decimal, it will be equal to one and 500ths or 1.05. And if we multiply that by 40, we get 42. Now, notice that our final answer is more than the original number we started with. 42 is more than 40. So let's summarize all that. In other words, we could say that 100% represents the total amount or the whole amount of the number that we started with. If we have less than 100%, that represents less than the total, so our answer will be less than the number that we started with. And more than 100% represents more than the total, so our final answer will be more than the number that we started with. So keep that in mind as you work on other problems, and that will give you an idea as to whether or not your answer makes sense.

Hi, I'm Mia!

With over 12 years of experience as a classroom teacher, tutor, and homeschool parent, my specialty is easing math anxiety for students of all ages. I'm committed to empowering parents to confidently support their children in math!

Copyright 2024 Solvent Learning