A short single-speaker YouTube tutorial (speaker: Felicity) explaining how to add mixed numbers. It demonstrates the simple case where fraction parts share a common denominator (example: 2 1/4 + 3 2/4 = 5 3/4) and the general case where denominators differ by converting mixed numbers to improper fractions (11/4 and 7/2), finding a common denominator (convert 7/2 to 14/4), adding to get 25/4, then converting back to the mixed number 6 1/4.
Questions this video answers
Felicity.
5 3/4.
2 3/4 + 3 1/2 → 6 1/4.
Chapters
Hi, I'm Felicity, and today we're going to be looking at adding mixed numbers. As we know already, a mixed number consists of a whole number and a fraction part. When we're adding mixed numbers that have a common denominator in the fraction part, it's really simple. So let's just look at a quick example. Here we've got two and one quarter, and we've got three and two quarters. Because the fraction part denominators are the same, all we need to do is first add the whole numbers to give us five, and then just add the numerators of the fraction parts to give us three. So we're left with five and three quarters. However, when the denominators of these fraction parts aren't the same, it's a little bit more complicated. So let's have a look at an example like this. So here I've got two wholesale and three quarters, and I have three wholes and one half. In order to add these together, we need to make them first into improper fractions. This is something we've looked at in a previous video. So we know that 2 wholes and 3/4 as an improper fraction can be written as 11/4. And then if we move on to this mixed number, we know that 3 wholes and 1/2 as an improper fraction can be written as 7 halves. At this point, you need to ask your students, can we add these two fractions together as they are? The answer is no, because they don't have a common denominator. You need to find a common multiple to create a common denominator. In this case, let's use 4 because it's a common multiple for these two numbers. So if we leave this one as 4, we can leave the top as well. However, to create this common denominator, we need to times it by two, and we need to treat the numerator in the same way. So seven times two is 14. Now, because we have a common denominator, all we need to do is add the numerators together. So we have 11 plus 14, which gives us 25 quarters. Now, finally, we need to express this as a mixed number to get our final answer. So what we do is divide the numerator by the denominator to give us six wholes and one quarter left over. And that's how you add mixed numbers.
