(upbeat music) - [All] Math Mights.

- Welcome 2nd grade Math Mights, I'm so excited that you've joined us for some math today.

My name is Mrs. McCartney, we have so many fun activities planned for today.

Today, we're going to do a mystery math mistake, and then we're going to match visual models to word problems.

Let's start off warming up our brain with a mystery math mistake.

Oh no, what's happened to all of our Math Mights?

All their strategies are all mixed up, we need your help.

Here's how the mystery math mistake works.

We have someone from Mathville that's all confused.

We're gonna show you this strategy, but you have to use your magnifying glass to think about where they made the mistake.

We need to come to the rescue and help them to solve the problem correctly using number sense.

Let's see who we have today with us.

We have our friend DC, who's upside down and all turned around.

He's trying to solve the problem 29 plus 58, and he think it equals 77.

He decided to decompose the 29 into 27 and two.

It looks like he was on the right track, but do you agree or disagree with the way DC got his answer?

I'm not sure.

Let's see what our friends, Jameson and Josiah are thinking.

Our friend Jameson said, "I think DC decomposed the 29 correctly.

I know if I add 27 plus two, it totals 29."

That's correct, if I look down at the 29 plus the 58, I think I understand what Jameson was saying.

He wanted to decompose that 29 into 27 and two, probably because he wanted to make that friendly number 60.

When DC went to add this together, he did get this total of 60 plus the 27.

When he added these two together, he had that total he showed of 77.

So, I agree with Jameson, he is onto something, he did decompose correctly.

So are we thinking that DC doesn't have a mistake?

Let's see what Josiah is thinking.

Our friend Josiah said, "I agree, he decomposed correctly.

I think he added incorrectly, when he put the numbers back together, 60 plus 27 equals 87 not 77."

Did you notice what Josiah noticed?

That was really good thinking.

Let's check it out down here and see.

If we were to add 60 plus 20 even though it's a two, we know it's worth two tens, that would equal 80.

And then we add the seven.

You're right, when he was adding, he added incorrectly.

Our answer is not 77, we know that it's 87.

When we work through the process of addition, sometimes we can make errors.

The mystery math mistake means that you're becoming a detective to find mistakes in math, and learning how we can solve them correctly?

I know DC would be so proud of our help today because he really needed it, he had an error in his addition.

Let's check out the I can statement for the day.

It says I can match word problems, visual models and expressions.

Take a look at these four images, A, B, C, and D. I want to know which one of them you think doesn't belong?

These look a lot like our visual models that we've been working on in 2nd grade, but I also see a number sentence.

Let's see what our friends, Josiah and Jameson have to say.

Our friend Jameson says, "A doesn't belong because it's the only one that doesn't show 27.

It shows the smaller part first."

Let's take a look here, as we look on these different diagrams with what Jameson has said.

I can see what he's talking about, this one has 27 at the beginning, 27 at the beginning, and 27 at the beginning.

But this part is showing 13 or like he said the smaller part.

That's a really great thing to notice as to why that one might not belong?

Our friend Josiah said, "B doesn't belong because it's the only one that doesn't show an unknown addend."

This is an unknown addend, we know because it's missing a part, 27 plus equals 40.

This also is a missing addend, 13 plus equals 40.

And same thing here, we have 27 plus equals our 40.

When Josiah is looking at this one, he's seeing it more as like a part-whole addition problem, where we're given the two parts and have to come up with the total.

Let's see if there's any more reasons why the boys might think C and D doesn't belong?

Our friend Jameson said, "D doesn't belong because it's the only one that is not a diagram."

He is correct.

These are interrelated with the two numbers, but this one here is showing the equation for us to solve for the missing addend, while the rest of these are all visual models.

Our friend Josiah says, "C doesn't belong because it's the only one that doesn't show a part-part-whole, it shows a comparison."

If we look here, this is on one bar and this is on one bar.

If I even want to do this, it could be on one bar, but this one is comparing two different parts.

Like is if somebody has 27 of something and another person has 40 of something.

This is known as an additive comparison bar, when we're doing word problems.

If you look at the other ones, we talked about this one being a part-whole addition, this is a part-whole missing addend.

These are all really great things.

I feel like we noticed a lot by picking out why each of these might not belong?

Here I have two word problems, two visual models, and two expressions.

It's our job to read the problems to see if we can match them?

Our first problem says, Elena gathered some apple seeds and 39 orange seeds.

She gathered 52 seeds all together.

How many apple seeds did she gather?

Do you think that this problem matches this visual model, or this visual model?

It's important when we're doing visual models, to take a closer look what the words are asking, to see if we can find the correct visual model to match up?

Elena gathered some apple seeds, well, maybe the sum is right here.

39 orange seeds, that could be true, and 52, oh, oh, it says altogether.

Do you think that 52 in that visual model is representing these all together?

I don't think so, because this is shorter.

I'm guessing that this visual model might not match.

Let's check our next visual model.

Elena gathered some apple seeds, 39 orange seeds, and 52 all together.

How many apple seeds did she gather?

I think it's important to label our visual models so we know exactly what the problem is asking?

Let's add those details now.

This said that Elena gathered some apple seeds, that's what our question mark is for, so I'm gonna go ahead and put an A for apple.

We don't know what kind, is it an apple tree?

No, we wanna label it seeds, so let's put seeds here.

What does this box represent?

Well, we know that represents the orange seeds.

Altogether, she created or collected 52 seeds.

The question mark here is asking, how many apple seeds did she gather?

Now it's time to figure out which expression will match to solve this problem.

Do you think it should be 52 plus 39, or something plus 39 equals 52?

Well, hopefully you picked the one that has the question mark, because it matches our tape diagram, our visual model right here.

We have the quest something, plus 39 equals 52.

We're not trying to add the two parts together, because she had a total of 52.

Now, obviously when we look at this top one, it should match the visual model, but let's double-check, Elena gathered 52 orange seeds, that must represent this bar up here.

She gathered 39 more apple seeds than orange seeds.

That's that 39 that we see here.

The question mark's at the end, 'cause it's asking how many apple seeds?

Let's go ahead and label these by putting that this bar represents the orange, and that this bar represents the apple.

Obviously, if we were to add these two together, these bars are equal, so our 52 plus 39 would be the expression that matches for this word problem and visual model.

Great job matching up the visual models, word problems, and the expressions.

It's a lot of attending to detail, but I think you did a great job.

I have another challenge for us.

I'm gonna show you this picture.

This game might remind you of a game that you've played called Mancala.

This game is a really great strategy game to play in math.

We had some friends create visual models that go with stories based on how they were doing when they were playing?

I want you to take a look at these two visual models.

I want you to see that these students were playing, instead of with marbles, they were playing with seeds.

We were able to draw one visual model, and another one.

What I want you to do is to be able to create the word problem, that goes along with this visual model.

I've added some details.

The reason I've added the details is because I think it's easier, if you label your visual models in 2nd grade, to help you figure out word problems.

Let's try the first one together.

This one says seeds, so that means boys and girls, this whole box is all about seeds.

The total in visual models can at the end, sometimes you'll see them in brackets at the bottom, it's the same.

So we know from looking at this, that there was a total of 64 seeds.

They don't know how many they started with, but they won 36.

Do you think you could recite the word problem, that was used to draw this visual model?

Let's give it a try.

Someone started with some seeds at the beginning of the game, and then they won 36.

At the end of the game, they had a total of 64.

How many seeds did they start with?

This is complicated, but if you walk through the problem together, you can create it.

We know that something plus 36 equals 64, to solve this, this would be the expression that would match.

Let's see if you can take a look at this second visual model.

Do you think you can figure out what the word problem said to match the visual model that you see?

I have some labels for you, seeds, we know that whole bar equals 64.

Left and lost, ooh, and a diagonal slash.

Do you think from those clues it will help you?

Do you think you can tell someone what the word problem was?

Let's give it a shot.

This one says, someone started off with 64 seeds, but in the game they ended up losing 36.

How many seeds do they have left?

Look at that, we came up with a story problem to match our visual model.

Now that we have this all matched up, let's just go ahead and solve it to see what the answer is?

I'm gonna look at this one, 64 minus 36.

I'm gonna use my friend Springling and use the open number line, to start at 36 and stop at 64.

I like to count up, my next friendly decade number is going to be 40.

So if I have Springling hop, I know that I went four.

I'm gonna go wild and go from the 40 all the way to the 60, because I can skip count by tens when I'm in 2nd grade that far.

I know the distance between 40 and 60 is 20, and between 60 and four is four.

If I add this up, I know that the answer is 20, 24, 28.

We can check this because if we put 28 plus 36, it should also equal 64.

We've learned a lot about this strategy with missing addend, to use addition or subtraction.

Great job using a strategy to help us to solve those expressions.

Now it's your turn to do what we did today in the show.

You're going to play a matchup word problems, to visual models and expressions.

I know you'll do a great job.

2nd grade Math Mights, we've had so much fun together from our mystery math mistake, helping DC, and then doing more with word problems.

I sure hope to see you on another Math Mights episode soon.

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