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

Lesson 28: Dividing fractions word problems

# Dividing whole numbers & fractions: t-shirts

In this math problem, we learn how to calculate the number of baby T-shirts that can be made from 48 yards of fabric. Each T-shirt requires 4/5 yards of fabric. By dividing 48 yards by 4/5 and simplifying, we find out that 60 baby T-shirts can be produced from the given fabric. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• How could you use the relationship between the numerator and denominator of fractions equivalent to one-half to determine if a fraction is less than one-half?

MATH problem on my daughters homework.
(45 votes)
• Hi JoAnn,
The best way to do this type of problem is to get a common denominator and then compare the two values. For example, let's say the question ask, "Is 7/13 less than 1/2?" The common denominator would be 26, so our question becomes, "Is 14/26 less than 13/26?" We can know see that it is not. It is actually greater than 1/2.
(54 votes)
• for my sake math is mental abuse to humans
(24 votes)
• bro this is 100 human abuse
(7 votes)
• 1/2x +2/3 =1/6
(7 votes)
• You have to follow the rule KCC (Keep Change Change.) Example 48 divided by 4/5. You would keep the 48 as it is changing it to 48/1, change the division sign to multiplication, and change the 4/5 to 5/4. Therefore do 48/1 times 5/4. 48 times 5 is 240. 1 times 5 is 5. If we change the 240/5 to a mixed number it would be 48. Hope you understand!
(10 votes)
• 😒I don't Understand😭🤷 But it is cool😒
(14 votes)
• If u dont understand Try doing another explanation
(5 votes)
• When u do the repricol process you have to KCF but the thing I don't really understand is the pre-simply part
(11 votes)
• You don't have to do the presimplifying. I don't do it, but some people think it makes things easier.
(3 votes)
• There are 10 pretzels and 12 kids. What fraction did each kid receive?
(5 votes)
• 10/12 = 5/6. Each child got 5/6 of a pretzel.
(11 votes)
• my problem has a mixed number and a regular fraction. can you do a video explain that
(6 votes)
• bru like when is this going to come useful in my life like
(7 votes)
• I'm a little confused on how Sal does the cross-multiplying - I've seen it a few times but I don't fully grasp it. Could someone provide another explanation?
(3 votes)
• Cross multiplying is basically simplifying but before you get the final answer. You have to find a common factor between the two numbers you're cross-multiplying, for example: 3/7 x 8/9. You're going to find a common factor between 3 and 9, which is 3. So, divide 3 by 3; and 9 by 3. Once you replace the 3 and 9 with what you got by dividing, now you can multiply straight across. Hope this helps!
(3 votes)
• Why are we talking about baby's T-shirts?
(6 votes)

## Video transcript

A baby's T-shirt requires 4/5 yards of fabric, or 4/5 of a yard of fabric. How many T-shirts can be made from 48 yards? So what we want to do is we essentially want to say how many groups of 4/5 of a yard can we make with 48 yards? So you literally view this as we want to take 48 yards and divide it into groups of 4/5 of a yard, and say how many groups are there? Because each of those groups can make one to baby's T-shirt. If you give me 4/5 of a yard, one baby's T-shirt, so the number of groups of 4/5 is the number of babies' T-shirts. Now, when we divide by a fraction, we just have to remember that that is the same thing, that is completely equivalent to multiplying times the reciprocal of the fraction. So if we have 4/5 here, that'll be 5/4, the reciprocal. Now, you still might say, hey, I have a whole number here and a fraction, and you just have to remember any whole number can be written as a fraction. This is the same thing as 48/1 times 5/4. Now, we could just multiply it out at this point and figure out what 48 times 5 is and that'll be over 4, but that'll get big numbers and it'll be hard to kind of divide and all that, but we could divide at this stage right here. We could divide the numerator and the denominator by 4. Or we could say, look, this is going to be equal to 48 times 5, whatever that is, over 4. Now, let's divide the numerator by 4. Well, we could divide 48 by 4, and we will get to 12, and whatever we did to the numerator, we have to do to the denominator, so if we divide 4 by 4, we get 1. So then we're left with 12 times 5, which is equal to 60. 12 times 5, which is equal to 60/1, which is the exact same thing as 60. So you can actually make 60 children's or babies' T-shirts from 48 yards if each of them use 4/5 of a yard.