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.

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

How do u know when a word problem is multiplying fractions or dividing fractions

you do this and that you equal your head

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.

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

Staging content lifeboat

Course: Staging content lifeboat > Unit 14

Lesson 38: Multiplying fractions word problems

Multiplying fractions word problem: laundry

Name: Multiplying fractions word problem: laundry
Uploaded: 2013-08-08T21:40:09Z
Description: Learn how to solve word problems involving multiplication of fractions. Watch examples of real-life scenarios where fractions are multiplied, and practice applying the concept to solve similar problems.

Google Classroom

Learn how to solve word problems involving multiplication of fractions. Watch examples of real-life scenarios where fractions are multiplied, and practice applying the concept to solve similar problems. Created by Sal Khan.

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FlameArrow987
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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
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- 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.
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- david.dong
  Posted 8 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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Dagmar Rojas
Posted 8 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 8 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.
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How do u know when a word problem is multiplying fractions or dividing fractions
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- Shawn Henly
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  you do this and that you equal your head
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Why multiply? Shouldn't he subtract? To get what's left he should subtract.
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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".
  Comment on HannahTran2005's post “There are 2/3 cups of det...”
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Paarth Bamb
Posted 6 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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- Raymond
  Posted 6 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.
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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??
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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.
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  (2 votes)

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.