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### Course: Arithmetic (all content)>Unit 5

Lesson 21: Multiplying fractions

# Multiplying 2 fractions: fraction model

Visuals can be used to multiply fractions in a variety of ways, such as by using fraction models. By drawing rectangles and dividing them into equal parts, we can use an area model to multiply fractions. help to illustrate how the numerators and denominators of the two fractions interact to produce a product. Created by Sal Khan.

## Want to join the conversation?

• Ok. When you are simplifying or dividing, keep these in mind:
Any even number is divisible by 2, so if both the numerator and the denominator are even, then you can continue to simplify it by 2.
If the digits of a number add up to a multiple of 3, then it is divisible by 3. So when both the numerator and denominator are multiples of 3, then you can simplify it by 3.
Numbers ending in 5 or 0 are divisible by 5.
You can just continue to simplify fractions with the 2, 3, and/or 5; these usually should be sufficient. And when two or more fractions are getting multiplied, you can take the numerator of one fraction and use it to simplify another fractions denominator (which will make the final multiplication easier). For example, if you have (5/8)x(2/3), then first simplify it to (5/4)x(1/3)heres a tip
• If the last two digits of a number are divisible by 4, then the number is divisible by 4.
If the number ends in 0, it is divisible by ten.
The three rule works for nine as well.
Accept? Decline?
• I have no idea what he is talking about and I've watched this video 3 times
• It is pretty easy all you have to do is multiply both numerator and denominator.
• I did not understand any of this I need more details.
• 1/2 *1/4 is simple and applies in all other.

2*4 = 8
1*1 = 1

therefore 1/2*1/4 = 1/8
if you wanted to do 2/3 * 5/7 it's the same.

multiply the denominator by the denominator and the numerator by the numerator.

2*5 = 10
3*7 = 21

therefore it is 10/21.

I hope you get it now.

numerator * numerator
denominator * denominator.
:)
• I keep getting stuck on the practice problems even though I have watched it at least 5 times.
• Same ;-; I keep having the same problem and the calculator has failed me.
• When solving this type of simple math do we really need to understand it visually or conceptually?
• I think it helps to understand it both ways. For example if you can teach the math to someone else, then you really understand all of it, which is I guess the goal. Of course, while you don't technically "need" to understand both, especially with the simpler parts of math it is often very helpful seeing as the harder math usually includes many of the same concepts and if you don't understand all the aspects then that makes it harder to learn higher maths.
• Is it possible to have a fraction as a numerator or denominator? Just curious.
• Yes, its possible. But it would be considered a complex fraction and would be simplified so the numerator & denominator became integers.
• this is so confusing!
• it is not confusing. Just multiply the numerators by the numerators and the denominators by the denominators, such as 1/2 * 1/4

2*4 = 8
1*1 = 1

and bingo 1/8 you're done. everyone complains it's hard. it really isnt. just follow the rule.

numerator * numerator (top number of the fraction
denominator * denominator (bottom number of the fraction)

(1 vote)
• What does "of" mean? Doesn't it just mean to multiply fractions? And if so, why don't the questions I answer on this site say the answers I put in are correct! AAAAAAAAAAA HELP ME PLEASE! (╯°□°）╯︵ ┻━┻
• "Of" means multiply so ex: 3 of 8/9