Video: Word Problems: Adding Numbers up to 20

In this video, we will learn how to solve addition problems with numbers up to 20 by finding either the missing part or the whole and how to solve additive comparison problems.

10:28

Video Transcript

Word Problems: Adding Numbers up to 20.

In this video, we’re going to learn how to solve addition problems with numbers up to 20. And we’re going to do this by finding either a missing part or the whole. We’re also going to find out how to solve addition problems where we have to compare. Here’s a word problem based on an addition. The first thing we need to do with it is to read through the problem carefully. Let’s try to imagine what it’s describing as we read through the words.

There are 14 trucks in a traffic jam. Eight are red and the rest are blue. How many trucks are blue?

We know that an addition is where two parts are added together to make the whole amount or the total. Now, what numbers do we already know in this word problem? Do we need to find one of the parts or the whole? Our first number tells us that there are 14 trucks in the traffic jam. This is the total amount, so we know the whole. And we also know what one of the parts is. Eight of the trucks are red. So let’s write the number eight in our part–whole diagram. Although we know how many trucks are red, we need to find how many trucks are blue. In other words, we need to find the other part.

To solve the word problem, we know we need to find a missing part of this addition. Eight plus what equals 14. What do we add to eight to make a total of 14? We could use a ten frame to help. Here are eight red counters. How many more counters do we need to get to 14? Let’s count on from eight. Nine, 10, 11, 12, 13, 14. We needed six more counters. Eight plus six makes 14. And now we can use this complete edition to answer our problem. The number of blue trucks is six.

All of the word problems we’re now going to look at have got either a missing part or a missing whole. Let’s try to find them.

A group of fairies were flying around a flower. After four more fairies joined the group, there were 14 fairies in total. How many fairies were there at the start?

This word problem doesn’t tell us how to find the answer. So we’re going to have to read it very slowly and carefully to work out what we need to do. The first sentence in our problem tells us that a group of fairies were flying around a flower. Now, we could look at the picture and think to ourselves, “That must be the group!”. But if we carry on reading the problem, we can see that this first group is only part of the whole amount. And we know this because four more fairies joined the group. So we start with a group and we don’t know how many are in that group. And then four more fairies joined the group.

We’re then told that after these four more fairies joined the group, there are 14 fairies in total. This is the whole amount. And if we look carefully at our picture, we can see that this is the amount that our picture shows. We can see four fairies wearing green dresses. These are the four more that joined the group. And if we look at the whole amount, we can see 14 altogether. To solve the problem, we need to find the missing part in this addition. What plus four equals 14.

Let’s use cubes to help us find the answer. One way to make the number 14 out of cubes is to take a group of 10 and then a group of four ones. 10 and four make 14. And because we know this number fact, we can now solve the problem. We know what the missing part in our addition is. Let’s put the number 10 into our word problem to see if it makes sense. A group of 10 fairies were flying around a flower. After four more fairies joined the group, there were 14 fairies in total. Yes, this does make sense. We know that 10 plus four equals 14. And so the number of fairies that were there at the start is 10.

Daisy planted seven roses and five sunflowers in her garden. Choose the addition sentence that shows this, using a question mark for the total number of flowers. Five plus what equals seven. Seven plus what equals 12. 12 plus five equals what. Seven plus 12 equals what. Or, seven plus five equals what.

In this problem, we’re given a fact using words. We’re told that Daisy, which is a good name when we talk about flowers, planted seven roses and five some flowers in her garden. We could use seven pink counters to represent our seven roses and five orange counters to represent the five sunflowers. We’re now told to choose the addition sentence that shows this. Well, if we’re thinking about adding together the number of roses and sunflowers, then each of these groups must be part of the whole.

So to find the whole or the total amount, we need to add the two parts together. In other words, seven plus five equals what. And if we look at all our possible addition sentences, we can see the one that represents this. The question mark represents the total number of flowers. And the way we can find the total number of flowers is by adding together seven and five. Perhaps you know what the total number is, but the question doesn’t ask us to work the answer out. We just need to find the correct addition sentence. And this is seven plus five equals what.

Michael is two years old. Benjamin is one year older than Michael. Madison is five years older than Benjamin. How old is Madison?

In this word problem, we’re asked to find the age of Madison. And if we read the word problem carefully, we can see a fact that will help us. We’re told Madison is five years older than Benjamin. But how old is Benjamin? If we look back through the word problem, we can find another fact that can help us. Benjamin is one year older than Michael. But wait a moment, how old’s Michael? To find the answer, we’re gonna have to go all the way back to the beginning. We’ll start with Michael’s age, and we’re going to find out everybody else’s age along the way.

So, let’s start with Michael. We’re told that he’s two years old. Let’s put a counter on our number track to show Michael’s age. In our next fact, we’re told that Benjamin is one year older than Michael. In other words, if we take Michael’s age, which is two, and we add one more year to it, then we can find Benjamin’s age. Two plus one equals what?

To find the answer, we could count on one from Michael’s age on our number track. We just need to move our counter one place. Two plus one equals three. So now we know Benjamin’s age; he’s three years old. And now we can solve our final fact because we’re told that Madison is five years older than Benjamin. Now we’ve just worked out, haven’t we, that Benjamin is three years old.

So we know Benjamin’s age. And we know that Madison is five years older than this. So if we add five and three together, this will give us Madison’s age. Three plus five equals what? Let’s count on five more using our number track. One, two, three, four, five. We’ve reached the number eight. Three plus five equals eight.

We’ve used two additions to solve this problem. Two plus one gave us Benjamin’s age, which is three. And then we took this answer, three, and we added five to it to find Madison’s age. Three plus five equals eight. And that’s how we know Madison is eight years old.

Let’s go over what we’ve learned in this video. We’ve learned how to solve addition word problems. We’ve learned how to find a missing part or the whole.

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