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2.Topic 3-Video 5

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In this video, we're going to learn what it means to divide whole numbers by unit fractions. Let's review what we already know about division. We know that when we divide whole numbers, we're taking a whole number and breaking it into equal size groups. There are 6 apples. And, each person gets 2 apples. We can figure out how many people will get apples, by using the division equation, 6 divided by 2. To solve this division problem, we first need to ask ourselves, how many groups of 2 are in 6 wholes. That means we need to take our 6 apples, and we need to put them into groups of 2. Now, we can count how many groups of 2 we have. You see we have 1 group of 2, 2 groups of 2, and 3 groups of 2. That tells us we have 3 groups of 2 in 6 wholes. And, 3 people can get apples. The 6, our total number of apples, is called the dividend. The 2, the number of apples in each group, in this case is called the divisor. 3, our answer, is called the quotient, and, it tells us, how many groups of 2 are in the 6. Let's look at this problem, in a different way. Let's say, we still have 6 apples. But, each person is going to get half of an apple, this time. We want to know how many people are there who will get apples. Well, now our division equation looks a little different. We have 6 divided by half. Instead of dividing 6 by a whole number, we are now dividing 6 by a fraction. One half is a unit fraction, because, the numerator is a 1. Any fraction with a numerator of 1, is called a unit fraction. In order to solve 6 divided by half, we need to ask ourselves, how many halves are in 6 wholes. In order to do that, we need to take our 6 whole apples, and we need to divide them into halves. Once I've done that, I can count how many halves I have in the 6 whole apples. Now, I'm going to count each half separately, because, each half is a group in this case. And, now I see that there are 12 groups of halves in 6 wholes. I want to make sure I write the answer to my problem, 6 divided by half, equals 12, and there's my problem was asking me how many people there were to get apples. I am going to label that, 12 people. Now, some of you, great mathematicians, may be noticing that your quotient, your answer is actually larger than the numbers you divided. You're absolutely right. That's because we divided a whole number by a fraction. Let's look at another problem. Let's say there are 3 cakes. And, each person is going to get one fourth serving of a cake. We want to know how many people will get cake. We can use the division equation 3 divided by one fourth to represent this problem. To solve this problem, we need to ask ourselves how many one fourth groups are in 3 wholes. To do that we need to slice each whole cake into fourths. Now, we can count how many groups of one fourth are there in these 3 wholes. I see that there are 1, 2, 3, 4, groups of one fourth in this 1 whole, which means there are 4 groups of one fourth in the others. Now, all I have to do is count by 4s, to make my counting quicker. So, I have 4... 4, 8, 12. I have 12 groups of one fourth which means 12 people can get cake. We can also use fraction bars to model this problem. The blue bars here represent our 3 wholes. The yellow bars represent how many groups of one fourth we have in those 3 wholes. Again, we see that in each whole there are 4 groups of one fourth. So, we have a total of 12 groups of one fourth. Let's look at one last problem. Say, I have 2 whole candy bars. And, I want to share those candy bars with some friends. So, I'm going to split or divide those candy bars into thirds. I have the problem, 2 divided by one third which means I nee to figure out how many groups of one third are in 2 wholes. All I need to do is count how many one thirds I see. And, I've seen 1, 2, 3, 4, 5, and, 6 groups of one third in the 2 wholes. Now, you've learnt what it means to divide a whole number by a unit fraction. You're now going to try some problems on your own.

Video Details

Duration: 5 minutes and 28 seconds
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Language: English
License: Dotsub - Standard License
Genre: None
Views: 5
Posted by: pgtranscribes on Apr 23, 2015

2.Topic 3-Video 5

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