I don't think this is correct because 2/3 = 4/6 and 1/2 = 3/6 so 4/6 subtract 3/6 = 1/6

Notice that Gina used half of the detergent, not half a cup of detergent. She started with 2∕3 cup and used 1∕2 of it, i.e. she used (1∕2)(2∕3) = 1∕3 cup. Thereby she'd be left with 2∕3 − 1∕3 = 1∕3 cup.

Why do you teach negative fractions to little kids in 5th grade

To some students, they will be ready to take pre-algebra in sixth grade, therefore advancing to higher level math courses. Negative fraction is a foundation to future concepts that teachers would expect from high level classes.

Simple. For example, 2/4 = 1/2 because you halve the numerator and the denominator to the simplest fraction possible.

Sal chose the fourth option but, as they said how much detergent will be left, we can to choose the first option because it makes more sense. Why did sal choose the fourth option instead of the first one??

In the first option, they're saying 2/3 MINUS 1/2. We are trying to find the answer for 2/3 TIMES 1/2. Hope this helps.

Why multiply? Shouldn't he subtract? To get what's left he should subtract.

There are 2/3 cups of detergent and she uses 1/2 of it. She uses 1/2 of the detergent that she has, not 1/2 half of a cup. Usually, when you're trying to find a proportion of something, you're multiplying. The key word for multiplying is "of".

Sal said, "She used a third of her detergent and has a third left". She actually used a 1/2 of her detergent.

Sal said she used a third CUP of her detergent, which is equal to a half of her detergent before she used it. As in, a half of 2/3 cups is 1/3 cup.

Main content

5th grade

Course: 5th grade > Unit 6

Lesson 6: Multiplying fractions word problems

Multiplying fractions word problem: laundry

Name: Multiplying fractions word problem: laundry
Uploaded: 2013-08-08T21:40:09Z
Description: Sal solves a word problem by multiplying 2 fractions.

CCSS.Math:

5.NF.B.6

Google Classroom

Sal solves a word problem by multiplying 2 fractions. Created by Sal Khan.

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FlameArrow987
Posted 5 years ago. Direct link to FlameArrow987's post “I don't think this is cor...”
I don't think this is correct because 2/3 = 4/6 and 1/2 = 3/6 so 4/6 subtract 3/6 = 1/6
Button navigates to signup pageComment on FlameArrow987's post “I don't think this is cor...”
(4 votes)
Answer
- Jerry Nilsson
  Posted 5 years ago. Direct link to Jerry Nilsson's post “Notice that Gina used hal...”
  Notice that Gina used half of the detergent, not half a cup of detergent.
  
  She started with 2∕3 cup and used 1∕2 of it,
  i.e. she used (1∕2)(2∕3) = 1∕3 cup.
  Thereby she'd be left with 2∕3 − 1∕3 = 1∕3 cup.
  Comment on Jerry Nilsson's post “Notice that Gina used hal...”
  (8 votes)
Rhys westover.
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i have no upvots
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Dagmar Rojas
Posted 7 years ago. Direct link to Dagmar Rojas's post “Why do you teach negativ...”
Why do you teach negative fractions to little kids in 5th grade
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- Angela G
  Posted 7 years ago. Direct link to Angela G's post “To some students, they wi...”
  To some students, they will be ready to take pre-algebra in sixth grade, therefore advancing to higher level math courses. Negative fraction is a foundation to future concepts that teachers would expect from high level classes.
  Button navigates to signup page
  (6 votes)
Rhys westover.
Posted 22 days ago. Direct link to Rhys westover.'s post “upvote me plz”
upvote me plz
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. .
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TristanR
Posted 6 months ago. Direct link to TristanR's post “how do you simplfy”
how do you simplfy
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- david.dong
  Posted 2 months ago. Direct link to david.dong's post “Simple. For example, 2/4 ...”
  Simple. For example, 2/4 = 1/2 because you halve the numerator and the denominator to the simplest fraction possible.
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  (2 votes)
madhav4movies
Posted 3 years ago. Direct link to madhav4movies's post “Sal chose the fourth opti...”
Sal chose the fourth option but, as they said how much detergent will be left, we can to choose the first option because it makes more sense. Why did sal choose the fourth option instead of the first one??
Button navigates to signup pageComment on madhav4movies's post “Sal chose the fourth opti...”
(2 votes)
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- Isabella Ricci
  Posted 3 years ago. Direct link to Isabella Ricci's post “In the first option, they...”
  In the first option, they're saying 2/3 MINUS 1/2. We are trying to find the answer for 2/3 TIMES 1/2. Hope this helps.
  Button navigates to signup page
  (2 votes)
Foxrii
Posted 5 years ago. Direct link to Foxrii's post “Why multiply? Shouldn't h...”
Why multiply? Shouldn't he subtract? To get what's left he should subtract.
Button navigates to signup pageComment on Foxrii's post “Why multiply? Shouldn't h...”
(1 vote)
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- HannahTran2005
  Posted 5 years ago. Direct link to HannahTran2005's post “There are 2/3 cups of det...”
  There are 2/3 cups of detergent and she uses 1/2 of it. She uses 1/2 of the detergent that she has, not 1/2 half of a cup. Usually, when you're trying to find a proportion of something, you're multiplying. The key word for multiplying is "of".
  Button navigates to signup page
  (4 votes)
Paarth Bamb
Posted 5 years ago. Direct link to Paarth Bamb's post “Sal said, "She used a thi...”
Sal said, "She used a third of her detergent and has a third left". She actually used a 1/2
of her detergent.
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(0 votes)
Answer
- Raymond
  Posted 5 years ago. Direct link to Raymond's post “Sal said she used a third...”
  Sal said she used a third CUP of her detergent, which is equal to a half of her detergent before she used it.
  
  As in, a half of 2/3 cups is 1/3 cup.
  Comment on Raymond's post “Sal said she used a third...”
  (4 votes)
Antartasim
Posted 7 years ago. Direct link to Antartasim's post “How do u know when a word...”
How do u know when a word problem is multiplying fractions or dividing fractions
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(3 votes)
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- Shawn Henly
  Posted 7 years ago. Direct link to Shawn Henly's post “you do this and that you ...”
  you do this and that you equal your head
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  (1 vote)

Video transcript

Gina had 2/3 cups of laundry detergent. She used half of the detergent on Friday to wash all of her sheets. How much detergent does she have left? So we're essentially going to take half of 2/3, or 1/2 times 2/3. So let's see which of these choices match up. So we should be taking 1/2 times 2/3. Well, here they're taking 2/3 minus 1/2, so this isn't going to be right. Here they're going to be taking-- let's see, 1/3, because 2/3 times 1/2, this is exactly what we want to do. We want to take half of 2/3. And we multiply the numerators, 2 times 1 is 2. Multiply the denominators, 3 times 2 is 6. You have 2/6. You could say the 2/6 has either been used up or 2/6 is left. And 2/6 is the exact same thing as 1/3. Divide the numerator and the denominator by 2, so this looks right. And so here 1/6 cup, well, we know it's not 1/6 cup. We know it's 1/3 cup. So here, 1/3 cup, because 2/3 is equal to 1/3 plus 1/3, that's right. So half of 2/3 must be 1/3. This is exactly right as well. These are both completely reasonable ways to getting to the right answer that Gina has 1/3-- she used 1/3 of a cup of laundry detergent, and she has 1/3 left.

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