How do you do Cross redusucing?

Good explanation here : https://www.youtube.com/watch?v=psWT_2QiAVc

how do you multiply negative fractions

Multiply the fractions normally, and ensure that the product has the correct sign. 1/2 * 1/2 = 1/4 (Two positives equal a positive.) -1/2 * -1/2 = 1/4 (Two negatives equal a positive.) -1/3 * 1/3 = -1/9 (A negative times a positive produces a negative .) 1/3 * -1/3 = -1/9 (The product will be negative, whether the negative number comes first or second.)

Why do you always have to simplify?

So the fraction reduced to lowest terms. When we reduce or simplify the fraction, we are writing a fraction in an equivalent form that may be easier to work with.

In the Multiplying Fractions Review, why is 5/6 x 5/7 clumped together as 5 x 5 with a single line below both and then 6 x 7 also brought together. It seems like an unnecessary step or is there a special meaning to doing this?

It's just a reminder that when multiplying fractions, we multiply numerator to numerator and denominator to denominator.

How do you multiply the single number with the mixed number?

You multiply a single number by a mixed number by putting a 1 under the single number.For example 2 + 3 1/2 your new equation would be 2/1 + 3 1/2. This is because 2/1 is the SAME exact thing a 2.

Main content

Arithmetic (all content)

Course: Arithmetic (all content) > Unit 5

Lesson 21: Multiplying fractions

Multiplying fractions review

Google Classroom

Review the basics of multiplying fractions, and try some practice problems.

Multiplying fractions

To multiply fractions, we multiply the numerators and then multiply the denominators.

Example 1: Fractions

empty space, start fraction, 5, divided by, 6, end fraction, times, start fraction, 5, divided by, 7, end fraction

equals, start fraction, 5, times, 5, divided by, 6, times, 7, end fraction

equals, start fraction, 25, divided by, 42, end fraction

Example 2: Mixed numbers

Before multiplying, we need to write the mixed numbers as improper fractions.

2, start fraction, 2, divided by, 3, end fraction, times, 1, start fraction, 3, divided by, 5, end fraction

equals, space, start fraction, 8, divided by, 3, end fraction, times, start fraction, 8, divided by, 5, end fraction

\qquad

[How do we write a mixed number as a fraction?]

equals, start fraction, 8, times, 8, divided by, 3, times, 5, end fraction

equals, start fraction, 64, divided by, 15, end fraction

We can also write this as 4, start fraction, 4, divided by, 15, end fraction .

Want to learn more about multiplying fractions? Check out this video.

Cross-reducing

Cross-reducing is a way to simplify before we multiply. This can save us from dealing with large numbers in our product.

Example

empty space, start fraction, 3, divided by, 10, end fraction, times, start fraction, 1, divided by, 6, end fraction

equals, start fraction, 3, times, 1, divided by, 10, times, 6, end fraction

equals, start fraction, start cancel, 3, end cancel, start superscript, 1, end superscript, times, space, 1, divided by, 10, times, start cancel, 6, end cancel, start subscript, 2, end subscript, end fraction

[Explain]

equals, start fraction, 1, divided by, 20, end fraction

Prefer a visual understanding of fraction multiplication? Check out one of these videos:
Multiplying 2 fractions: fraction model
Multiplying 2 fractions: number line

Practice

Problem 1

Current

start fraction, 5, divided by, 8, end fraction, times, start fraction, 7, divided by, 8, end fraction

Want to try more problems like this? Check out these exercises:
Multiply fractions
Multiply mixed numbers

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🐼 Nylah🐼
Posted 6 years ago. Direct link to 🐼 Nylah🐼's post “How do you do Cross redus...”
How do you do Cross redusucing?
Button navigates to signup pageComment on 🐼 Nylah🐼's post “How do you do Cross redus...”
(33 votes)
Answer
- dave
  Posted 3 years ago. Direct link to dave's post “Good explanation here : h...”
  Good explanation here : https://www.youtube.com/watch?v=psWT_2QiAVc
  Button navigates to signup page
  (4 votes)
Blake Mcgill
Posted 6 years ago. Direct link to Blake Mcgill's post “how do you multiply negat...”
how do you multiply negative
fractions
Button navigates to signup pageComment on Blake Mcgill's post “how do you multiply negat...”
(28 votes)
Answer
- Anthony Fritz
  Posted 6 years ago. Direct link to Anthony Fritz's post “Multiply the fractions no...”
  Multiply the fractions normally, and ensure that the product has the correct sign.
  
  1/2 * 1/2 = 1/4 (Two positives equal a positive.)
  -1/2 * -1/2 = 1/4 (Two negatives equal a positive.)
  
  -1/3 * 1/3 = -1/9 (A negative times a positive produces a negative .)
  1/3 * -1/3 = -1/9 (The product will be negative, whether the negative number comes first or second.)
  Comment on Anthony Fritz's post “Multiply the fractions no...”
  (22 votes)
SG
Posted 5 years ago. Direct link to SG's post “Why do you always have to...”
Why do you always have to simplify?
Button navigates to signup pageComment on SG's post “Why do you always have to...”
(15 votes)
Answer
- ckovell
  Posted 5 years ago. Direct link to ckovell's post “So the fraction reduced t...”
  So the fraction reduced to lowest terms. When we reduce or simplify the fraction, we are writing a fraction in an equivalent form that may be easier to work with.
  Button navigates to signup page
  (12 votes)
Mustafa
Posted 5 years ago. Direct link to Mustafa's post “What is GCD? thanks to wh...”
What is GCD? thanks to whoever answers it
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(11 votes)
Answer
- Swift
  Posted a month ago. Direct link to Swift's post “greatest common denominat...”
  greatest common denominator= GCD
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  (1 vote)
ealphonse1
Posted 5 years ago. Direct link to ealphonse1's post “What is the difference be...”
What is the difference between LCD and LCM.
Button navigates to signup pageButton navigates to signup page
(8 votes)
Answer
- Kalabi
  Posted 8 months ago. Direct link to Kalabi's post “The mathematical approach...”
  The mathematical approach to finding the LCM and LCD is the same. For both, we need to find the least common multiple of two or more numbers. The least common denominator (LCD) is actually the least common multiple (LCM) of the denominators.
  Button navigates to signup page
  (1 vote)
daphne_hartman
Posted 6 years ago. Direct link to daphne_hartman's post “How do you multiply the s...”
How do you multiply the single number with the mixed number?
Button navigates to signup pageComment on daphne_hartman's post “How do you multiply the s...”
(4 votes)
Answer
- Emma Villescas
  Posted 4 years ago. Direct link to Emma Villescas's post “You multiply a single num...”
  You multiply a single number by a mixed number by putting a 1 under the single number.For example 2 + 3 1/2 your new equation would be 2/1 + 3 1/2. This is because 2/1 is the SAME exact thing a 2.
  Comment on Emma Villescas's post “You multiply a single num...”
  (5 votes)
emily_prickett
Posted 6 years ago. Direct link to emily_prickett's post “how do you get the top nu...”
how do you get the top number on the top like 3 times 2 2/5 how do you get 7 1/5
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(9 votes)
Answer
Mae Niemie
Posted 5 years ago. Direct link to Mae Niemie's post “In the Multiplying Fracti...”
In the Multiplying Fractions Review, why is 5/6 x 5/7 clumped together as 5 x 5 with a single line below both and then 6 x 7 also brought together. It seems like an unnecessary step or is there a special meaning to doing this?
Button navigates to signup pageComment on Mae Niemie's post “In the Multiplying Fracti...”
(5 votes)
Answer
- Kim Seidel
  Posted 5 years ago. Direct link to Kim Seidel's post “It's just a reminder that...”
  It's just a reminder that when multiplying fractions, we multiply numerator to numerator and denominator to denominator.
  Button navigates to signup page
  (13 votes)
Nathalie Figueroa
Posted 4 years ago. Direct link to Nathalie Figueroa's post “same what's a LCD? can yo...”
same what's a LCD? can you comment it pls or explan it better.
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(5 votes)
Answer
- Jae Chung
  Posted 3 years ago. Direct link to Jae Chung's post “If LCD means least common...”
  If LCD means least common denominator. What does LCM mean?
  Comment on Jae Chung's post “If LCD means least common...”
  (1 vote)
Lauren
Posted 5 years ago. Direct link to Lauren's post “I'm realy confused when i...”
I'm realy confused when it comes to math in general.
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(5 votes)
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