Ratios and Percentages

In this video, we’re going to talk about ratios and percentages. Now, a ratio is a way to compare two different quantities to one another.

So, for instance, let’s take: If we have 20 red, and 25 blue, we can say that the ratio of red to blue is 20:25.

 33%

Question 1 of 3

If a parking lot's SUV: sedan ratio is 1:3, what percent of the lot is cars and how many SUV's park in a 100-vehicle lot?

A. 33% and 33 SUV's

B. 40% and 40 SUV's

C. 25% and 25 SUV's

D. 75% and 25 SUV's

Question 1 of 3

Question 2 of 3

Kate is reading a book. The ratio of the number of pages she read to the pages that remain to be read is 7 : 3. If the book contains 500 pages in all, how many pages did Kate read?

A. She read 350 pages

B. She read 150 pages

C. She read 50 pages

D. She read 450 pages

Question 2 of 3

Question 3 of 3

A soup recipe calls for 7:5 in water:vegetables.  What percent of the soup volume is water, and how many cups of vegetables are needed for 60 cups of soup?

A. 67% water and 20 cups of veggies

B. 60% water and 25 cups of veggies

C. 60% water and 40 cups of veggies

D. 60% water and 24 cups of veggies

Question 3 of 3

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The next lesson: Calculation of a Percentage
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The transcript is provided for your convenience
And so, this is what ratio notation looks like. You have a number that represents the first quantity, and a colon, and then a number that represents the second quantity.

And so, this right here is not a proper ratio, because you can reduce it to a smaller number representation of the same idea. So, any time you have two numbers in a ratio that can both be divided by the same number, it’s not yet in a proper ratio format.

So, 20 and 25 can both be divided by 5. If we divide 20 by 5, we get 4, and if we divide 25 by 5, we get 5. So, the true ratio of red to blue is 4:5.

So, that’s kind of how ratios work. Percentages are also a way to compare two different things, but generally, these are used to compare a part of something to the whole.

So, let’s say that in this bag we also add 5 white. So, that means that the total number of in the bag is 20 plus 25 plus 5, or 50.

So, 50 in the bag is a whole, and there are 20 red, so we might wonder, what is the percentage of red in the bag? Generally, the way you want to approach this is you want to create a fraction, and then convert it to a percentage.

So, if we have 20 red, that’ll be our numerator, and we said we had 50 in the bag as a whole, so that will be our denominator. So, 20 red, 50 total.

So, this is our fraction of red total. In order to make this a percentage, we’ll have to multiply top and bottom by 2 to get the denominator equal to 100. So, multiply this by 2/2, and that’ll give us 40/100.

Now, a percentage is just another way to represent a fraction where the denominator is 100, so if we say 40%, that’s the same as saying 40/100. So, the percentage of red in the bag is going to be 40%.

This is how you write a percent. You write a number, and then this symbol, and that denotes 40% of the whole. And so, that is how you can use ratios and percentages for simple things.