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### Course: Pre-algebra > Unit 4

Lesson 1: Intro to percents# Percents from fraction models

Converting fractions to percentages is a valuable skill in math. To do this, rewrite the fraction with a denominator of 100, as "percent" means "per 100." For example, 7/10 equals 70/100, or 70%. Additionally, you can add percentages together, such as 100% + 80% = 180%.

## Want to join the conversation?

- ik the percent thing but i forget easliy and can get confused so just incase, can sombody explain this in a muck easier way? ;-;(25 votes)
*To change a fraction to a percent, all you have to do is change the denominator of the fraction to 100, and then figure out how you got there. For example, if I have 1/2, and I want to change it to a percent, I can change the denominator to 100, and then divide by my old fraction, aka just dividing 100 by 1/2, and then my answer (50) is my percent. Sorry if I confuse you more.*(25 votes)

- no way I got all of them right I think ¯\
*(ツ)*/¯(24 votes) - what si 20% as a decimal(6 votes)
- To change any percent into a decimal, just divide by 100.

Give it a try.(12 votes)

- At0:13,1:39,2:22, and3:24he tells us to pause the video. Why does he do that?(4 votes)
- so you can learn it and then he explains it and you can check your answer:)(6 votes)

- how many time do you multiply(5 votes)
- It doesn't matter how many times you multiply, just what you multiply.(8 votes)

- What if it's not a square or a rectangle what if its a circle?(7 votes)
- the shape does not matter, as long as you can count the pieces and turn the fraction of that shape and pieces into a fraction over 100, you're good to go!(4 votes)

- how do i take the test for this video without the video saying "not started yet" ?(9 votes)
- wait how do you get the number to multiply by to turn the fraction to a percentage? if this was already said in this video, pls dont mind me I have ADHD. but atleast an answer?(4 votes)
- The idea is to rewrite the fraction as an equivalent fraction with denominator 100.

To do this, figure out what number to multiply the denominator by, to get 100. Then multiply the numerator by the same number.

Example: convert 3/5 to a percent.

First figure out what number to multiply the denominator 5 by, to get 100. Note that 5x2=10, and 10x10 = 100. So 20 is the number we need to multiply 5 by, to get 100.

Now multiply the numerator 3 by 20 to get 60.

So 3/5 = 60/100 = 60%.

The answer is 60%.

Have a blessed, wonderful day!(6 votes)

- i dont have a qstion(6 votes)
- this is easier than i thought!(5 votes)

## Video transcript

- [Instructor] So we're told the square below represents one whole, so this entire square is a whole. And then they ask us what
percent is represented by the shaded area, so why
don't you pause this video and see if you can figure that out. So let's see. The whole is divided into
one, two, three, four, five, six, seven, eight,
nine, 10 equal sections, of which one, two, three, four, five, six, seven are actually filled in. That's the shaded area,
so one way to think about it is 7/10 are shaded in, but how do we express this
fraction as a percent? They're asking for a percent. Well remember, percent, it
literally means per hundred. Cent, same root as the word 100. You see it cents or century,
and so can we write this as per 100 instead of per 10? Well, seven per 10 is the same
thing as 70 per 100, or 70%. And how did I go from 7/10 to 70 over 100? Well, I just multiply both the numerator and the denominator by 10. And once you do more and more percents, you'll get a hang of it. You'll say, "Oh, 7/10. "That's the same thing as
70 per 100, which is 70%." Let's do another example. Here, we're told 100% is shown on the following tape diagram, so just this amount
right over here is 100%, and then they ask us what
percent is represented by the entire tape diagram, so by this entire thing right over here. Pause this video and see
if you can answer that. Well, one way to think about 100%, 100% is equivalent to a whole,
and now we have three times as much as that for the
entire tape diagram, so you could view this as three wholes, or you could say that's 100%. We have another 100% right over here. And then we have another
100% right over here, so the whole tape diagram,
that would be 300%. Let's do another example. This is strangely fun. (laughs) Okay, and I'll see. It says the large rectangle
below represents one whole. All right, so that's this
whole thing is one whole. What percentage is represented
by the shaded area? So pause the video and see if
you can figure that out again. So let's just express
it as a fraction first, so we have a total of one,
two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 squares. So out of those 20
squares, we see that six of them are actually shaded in. So 6/20, could we write that as per 100? Well, let's see. To go from 20 to 100, I multiply by five, and so if I multiply
the numerator by five, I'll get the same value. Six times five is 30, so
six per 20 is the same thing as 30 per 100, which is
the same thing as 30%, which literally means
per 100, so this is 30%. Let's do one last example. Here we are told each large rectangle below represents one
whole, so this is a whole, and then this whole thing right
over here is another whole. What percentage is represented
by the shaded area? Again, pause the video. See if you can answer that. So this one, we've shaded
in a whole, so that is 100%, and then over here, we have shaded in one, two, three, 4/5 of the whole. So 4/5, if I wanted to express it as per 100, what would it be? Well, five time 20 is 100,
so four times 20 is 80, so 4/5, or 80/100, is filled out here. We could say 80 per 100, which
is the same thing as 80%, so this right over here is 80%. So what percent is represented
by the shaded area? Well, we have 100%, and then
we have 80%, so we have 180%. It's more than a whole. If you have a percentage
that is larger than 100%, you're talking about
something that is more than a whole, and then we see that. We have a whole right over here, and then we have 80% more than that.