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Lesson 3: Multiplying fractions

# Multiplying 2 fractions: 5/6 x 2/3

When multiplying fractions, you first start with the two fractions you want to multiply. You multiply the numerators (the top numbers) together, and then multiply the denominators (the bottom numbers) together. After putting the two results together as a new fraction, you may need to simplify the fraction in order to express it in its lowest terms. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• Is there another way to put answers in simplest form another way then the ones shown in the video? •   Yes. Lets say we have a question saying 5/3 x 10/5. You can simplify the two fives so it can become 1/3 x 10. This is easier to make it into simplest form.
• I still do not get it that much •  What would you do? well you would fist look at you numbers then you would put the numerator with the other numerator and the denominator with the other denominator.
(Sounds confusing,right?), so it would look something like this:
6/10 * 3/6 = 6*3(numerators)/10*6(denominators), so 6*3 is 18 so 18 is your numerator(for the answer), 10*6 = 60 so 60 is your denominator(for your answer). so the answer is 18/60, well that's a big number so lets simplify it, so you need to find a LCM(Least Common Multiple) witch is 6 so it would look like this 18(/)6/60(/)6= 3/10.

(* is times((/) is division)
If you still don't understand maybe watch the vidio a few time(then you start to understand).

• What do you do if the denominator is different from the other one? • this was helpful like if you have a good day! • At , I have always wondered why cant we simplify the denominators : 6 and 3 instead of the 6 and 2?? •  If you multiply or divide top and bottom of any fraction by the same number, you do not change the value of the fraction. If you modify only top or only bottom you are changing the value of the fraction.
Here are examples.
Let's say I have fraction 1/2. That's half.
I can multiply top and bottom by 2. (1*2)/(2*2) = 2/4. Now I made 2 quarters. Guess what? 2 quarters is one half. 1/2=2/4. This two fractions look different, but they represent the same value.

Take a pizza, divide it into 12 equal slices, take 3 slices. How much of pizza did you get? 3/12. I can divide top and bottom by 3. (3/3)/(12/3) = 1/4. Take a look at the 3 slices you got. You have a quarter of a pizza. So 3/12 = 1/4

In the video the fraction was (5 * 2) / (6 * 3). We can divide top and bottom by 2 and the value will not change. (5 * 2 / 2) / (6 * 3 / 2). 2 / 2 = 1 and 6 / 2 = 3. You'll get (5 * 1) / (3 * 3). That is what you've seen in the video.
Let's compare (5 * 2) / (6 * 3) = 10/18. Divide top and bottom by 2 you'll get 5/9. (5 * 1) / (3 * 3) = 5/9. The same!! If you take 2 pizzas and divide one into 18 equal slices and than take 10 slices, the other divide into 9 slices and take 5 of them, you'll get the same amount of pizza.
Let's take original fraction (5 * 2) / (6 * 3) and try to divide only the bottom part (5 * 2) / (6 / 3 * 3 / 3) = (5 * 2) / (3 * 1) = 10/3 That is totally different value. That fraction means 3 whole pizzas and one third of fourth pizza. This does not equal to our original fraction.
Lengthy explanation, but I hope it is helpful. • why do you make math so hard? its just so hard • If you multiply or divide top and bottom of any fraction by the same number, you do not change the value of the fraction. If you modify only top or only bottom you are changing the value of the fraction.
Here are examples.
Let's say I have fraction 1/2. That's half.
I can multiply top and bottom by 2. (1*2)/(2*2) = 2/4. Now I made 2 quarters. Guess what? 2 quarters is one half. 1/2=2/4. This two fractions look different, but they represent the same value.

Take a pizza, divide it into 12 equal slices, take 3 slices. How much of pizza did you get? 3/12. I can divide top and bottom by 3. (3/3)/(12/3) = 1/4. Take a look at the 3 slices you got. You have a quarter of a pizza. So 3/12 = 1/4

In the video the fraction was (5 * 2) / (6 * 3). We can divide top and bottom by 2 and the value will not change. (5 * 2 / 2) / (6 * 3 / 2). 2 / 2 = 1 and 6 / 2 = 3. You'll get (5 * 1) / (3 * 3). That is what you've seen in the video.
Let's compare (5 * 2) / (6 * 3) = 10/18. Divide top and bottom by 2 you'll get 5/9. (5 * 1) / (3 * 3) = 5/9. The same!! If you take 2 pizzas and divide one into 18 equal slices and than take 10 slices, the other divide into 9 slices and take 5 of them, you'll get the same amount of pizza.
Let's take original fraction (5 * 2) / (6 * 3) and try to divide only the bottom part (5 * 2) / (6 / 3 * 3 / 3) = (5 * 2) / (3 * 1) = 10/3 That is totally different value. That fraction means 3 whole pizzas and one third of fourth pizza. This does not equal to our original fraction.
Lengthy explanation, but I hope it is helpful.   