is multiplication of fractions same as adding fractions

Also, when you multiply two fractions less than one, your answer actually gets smaller. Think about the multiplication sign as saying "groups of." 3 x 8 = 24 means 3 groups of 8 are 24. With fractions, you're still saying that. 1/2 of a group of 12 is 6. 1/3 of a group of 9 is 3. The procedure for two fractions is to multiply across -- numerator times numerator and denominator times denominator. 1/2 x 2/3 is saying that you have half of a group that was 2/3 of a full group to begin with. So, you had 2 thirds, but not you only have half of that, or 1/3 numerators : 1 x 2 = 2 denominators: 2 x 3 = 6 So the answer is 2/6, which can be reduced to the equivalent fraction 1/3.

so 3/4 of an hour is 45 min right?

yes an hour has 60 min so 1/4 of an hour is 15 min so multiply that by 3 and you get 45

Does the end result have to be a mixed fraction?

Not always. It could be a decimal for example.

Main content

Staging content lifeboat

Course: Staging content lifeboat > Unit 14

Lesson 15: Adding and subtracting fractions: word problems

Fraction word problem: lizard

Name: Fraction word problem: lizard
Uploaded: 2013-08-08T20:31:07Z
Description: Sal solves a fraction word problem about the length of a lizard. The fractions have common denominators.

CCSS.Math:

4.NF.B.3

4.NF.B.3d

Google Classroom

Sal solves a fraction word problem about the length of a lizard. The fractions have common denominators. Created by Sal Khan.

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anapal
Posted 7 years ago. Direct link to anapal's post “is multiplication of frac...”
is multiplication of fractions same as adding fractions
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- jane.h.graves
  Posted 7 years ago. Direct link to jane.h.graves's post “Also, when you multiply t...”
  Also, when you multiply two fractions less than one, your answer actually gets smaller. Think about the multiplication sign as saying "groups of." 3 x 8 = 24 means 3 groups of 8 are 24.
  
  With fractions, you're still saying that. 1/2 of a group of 12 is 6. 1/3 of a group of 9 is 3.
  
  The procedure for two fractions is to multiply across -- numerator times numerator and denominator times denominator.
  
  1/2 x 2/3 is saying that you have half of a group that was 2/3 of a full group to begin with. So, you had 2 thirds, but not you only have half of that, or 1/3
  
  numerators : 1 x 2 = 2
  denominators: 2 x 3 = 6
  
  So the answer is 2/6, which can be reduced to the equivalent fraction 1/3.
  Comment on jane.h.graves's post “Also, when you multiply t...”
  (13 votes)
bananaman7230
Posted 5 years ago. Direct link to bananaman7230's post “so 3/4 of an hour is 45 m...”
so 3/4 of an hour is 45 min right?
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(9 votes)
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- NunYa Business
  Posted 5 years ago. Direct link to NunYa Business's post “yes an hour has 60 min so...”
  yes an hour has 60 min so 1/4 of an hour is 15 min so multiply that by 3 and you get 45
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  (9 votes)
izabela.jankech
Posted 2 years ago. Direct link to izabela.jankech's post “The lizard is very nice.”
The lizard is very nice.
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(10 votes)
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- 🐬🦩~Kuromi~🦩🐬
  Posted 3 months ago. Direct link to 🐬🦩~Kuromi~🦩🐬's post “yes it is”
  yes it is
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  (1 vote)
Tyler Stanley
Posted 9 years ago. Direct link to Tyler Stanley's post “Does the end result have ...”
Does the end result have to be a mixed fraction?
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(6 votes)
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- Krasy
  Posted 9 years ago. Direct link to Krasy's post “Not always. It could be a...”
  Not always. It could be a decimal for example.
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  (5 votes)
Leafy!!!!!!
Posted 7 years ago. Direct link to Leafy!!!!!!'s post “um did sal draw the lizar...”
um did sal draw the lizard (sorry if this was against the rules im just curious!) ?
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dmoreno-m0001
Posted 3 years ago. Direct link to dmoreno-m0001's post “I kind of get confused wi...”
I kind of get confused with the ruler thingy but it is very helpful, in fact I get it now just by looking at the problem so... nah.
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(7 votes)
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- 🐬🦩~Kuromi~🦩🐬
  Posted 3 months ago. Direct link to 🐬🦩~Kuromi~🦩🐬's post “ok its good that u unders...”
  ok its good that u understand it now so....yeah!
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  (1 vote)
madelynrball
Posted 8 years ago. Direct link to madelynrball's post “how can you ad the tail a...”
how can you ad the tail and body together shouldent it be head body and tail?
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(4 votes)
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kayden math
Posted a month ago. Direct link to kayden math's post “how did u draw it so good...”
how did u draw it so good on computer man?
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(4 votes)
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christian v
Posted 3 years ago. Direct link to christian v's post “you are teaching me so mu...”
you are teaching me so much it's just been hard in 5th grade.
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Khadiza
Posted a year ago. Direct link to Khadiza's post “i got confused on the las...”
i got confused on the last one
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(3 votes)
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Video transcript

James and Karlee caught a lizard in their backyard. Its body is 17/8 inches long, and its tail is 10/8 inches long. What is the length of the lizard's body and tail together? So good thing we have the lizard obediently standing next to our measuring stick or our ruler or whatever this happens to be. And we have it marked off in inches. And not only that, we have it marked off in eighths of inches. Notice-- this is an inch, and we have 1, 2, 3, 4, 5, 6, 7, 8 sections of that actual inch. So, let's see, 17/8 inches long. This is going to be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17. This right over here is 17/8, which you might notice is also equal to 2 and 1/8. 8 goes into 17 two times with a remainder of 1. But we won't talk about that just yet. But we see that's the length of the lizard's body-- 17/8. I just counted off 17 of these 8's right over here-- 17/8. And then they say that the tail is 10/8 inches long. So it's another 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. So this distance right over here, I just counted off 10/8. So that's another 10/8 inches long, and it gets us all the way to the end of the lizard's tail. And they say what is the length of the lizard's body and tail together? Well, that's going to be the length of the body plus the length of the tail. So you have 17/8 plus 10/8. Well, that's going to get you to 17 plus 10/8, which is equal to 27-- 27/8. And so this mark right over here is 27/8. And if you wanted to write this as a mixed number, you could just say, well, 8 goes into 27 three times, and you have a remainder of 3. So this is equal to 3 and 3/8. And you see that on the ruler right over here. It's equal to 1, 2, 3. And then we have another 1, 2, 3/8. These two things are equivalent.