(upbeat music) - [Kids] Math mights!

- Welcome, second grade math mights, my name is Mrs. McCartney.

I'm so excited that you've joined us today to learn about math.

Let's check out our plan for today.

Today, we're gonna do a mystery math mistake, and then we're gonna learn about coins and their values.

Let's start off first with warming up our brain with a mystery math mistake with our friends from the math mights.

Oh no, what's happened to all of our math might friends?

They're all messed up and turned around with their strategies.

Oh no, we're gonna have to help them out as we start to look at our strategy today, to see if you can find the mystery math mistake.

I have a friend that's told me how they solved the problem.

And what we're gonna do is have you put your magnifying glass so you can look up close at that problem to see if you can find where one of our math might friends made a mistake.

The problem we're gonna look at today is this problem, it's 78 plus 14.

We're gonna solve this problem with our friend, T Pops.

T Pops is upside down, and may have an error.

So be sure to keep your eyes out to see where his mistake might be.

I have T Pops' place value mat here so we can really demonstrate how to do the traditional method.

I have 78 plus 14.

T Pops wanted me to show you how he did this, so I want you to see if you can find the mistake.

We're gonna take our eight, and we're going to add an additional four.

When we add this together, we can see that we have 10 and two, which is equals 12 or 12 ones.

We can't fit all of these into the ones column, so we're going to put our two ones here and bring our one 10 here.

You can still see that 12, one 10, and two ones.

So we're gonna take our discs to rename our number with one 10, and two ones.

Now, we're gonna add together our tens, 70 plus 10, which you can see here.

We have 70, and I'm gonna add on an additional 10 to get the total of 82.

T Pops thinks 78 plus 14 equals 82.

Did you find the mystery math mistake while we were solving that from T Pops?

Or do you think that that problem is just solved correctly?

Let's see what our friend, Nora and Laila think.

Nora says, "When you do 82 minus 14, I don't get 78.

"Something's not correct here."

Does Nora's statement make sense to you?

It sounds like she's doing the inverse operation to check the math.

Let's check it out to see if Nora is correct.

Nora said, if I subtract 82 minus 14, it doesn't equal 78.

We know if we have addition, and we take our sum and subtract it from one of our add-ins, we should get our other add-in.

And she is correct, when we do 82 minus 14, we do not get 78, we get 68.

Let's see what our friend Laila thinks.

Laila says, "It looks like you added the ones correctly.

"However, when you added the tens, "you forgot to add in the 10.

"So, the answer would be 92."

Let's go back and take a look at our mat to see if we can make that correction that Laila's talking about.

We started off with 78, and we wanted to add 14.

One, two, three, four.

I see where we have our one 10, and our two ones because these 10 ones make up the one 10.

When we go to take these off, we have to rename 10 ones as one 10, and bring it over.

Laila's correct, we did not do that last time I took these off, but we didn't rename the number by putting it in the tens column to see our 10 and two ones that you see here.

Now when it's time to add the 70 plus the next 10, and the new 10 we added, we get the total of 92, which that makes a lot of sense as we look at that problem.

Did you see that mystery math mistake as we were solving the problem too?

We really have to think about where we see errors in math.

That tells us we're becoming master mathematicians.

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

I can learn about coins and their values.

Let's brainstorm a minute about money.

What do you know about money?

Did you learn anything about money when you were in first grade?

Have you seen money used maybe at the store, or have you seen any money lying around your house?

Let's talk first about what we know about money.

The first one is that we know that we can buy things with money.

Another one of our friends has noticed that some money is made out of paper.

Another friend says coins are different sizes and colors, and most of them are silver.

Our last friend says, a quarter is 25 cents.

I bet that you could add more things to our poster about what you know about money.

Today, we're gonna talk about money as it relates to coins and their values.

Let's take a look at these coins first, show me the money!

Andre has these coins.

What is the name of the coins that he has?

Are they nickels, dimes or pennies?

Have you seen this coin before?

Let's check it out.

Andre was actually holding a dime.

I have a dime here in my hand.

It's one of the smallest coins that you'll see.

When we look at dimes, you can see that they have a head, and it has a tails.

Now, a dime's kind of small to see, so I blew up Andre's dimes here.

A dime is worth 10 cents.

Let's skip count by tens together to find the value.

10, 20, 30, 40, 50, 60, 70 cents.

I know that seven dimes equals 70 cents because we were able to count by tens.

Do you know what dimes remind me of?

They remind me of our place value disks that we were just using in the T Pops place value mat.

Let's take a look at it here.

This is actually showing the value of what the dimes are to help us know to skip count by 10.

Let's check out another coin to see if you know what the coin is.

On here we have Han's coins.

What is the name of his coins?

Are they nickels, dimes or pennies?

What is the value of his coins?

The coins that Han has are nickels.

Nickels are silver.

They're a little bit larger than a dime.

However, it's kind of weird, they're worth less.

They're only worth 5 cents.

Here I have Han's coins blown up, and we have the actual size of the coin.

You can also see that there are heads and there are tails.

This will be easy because we can skip count by fives to find the value.

Five, 10, 15, 20, 25, 30, 35.

We see that seven nickels equals 35 cents.

Wow, we were able to count sets of coins.

I don't know if you noticed, but they all had seven coins, but they didn't equal the same value.

So we have to be careful as we're starting to learn coins, to look to see which coin is which, and how much their value is.

Let's talk more about how we can show two different ways to make 10 cents.

Our friend Nora says, "I think that two nickels could equal 10 cents," but our friend Laila has a different idea.

Let's take a look here.

I have 10 cents, but I did not put a dime.

Nora thought that maybe two nickels could equal the 10 cents, five, 10, she's correct.

A dime or 10 cents could also be represented the way Laila thought of it.

She thought of it as a nickel and five pennies.

So we would count five, six, seven, eight, nine, 10 cents, two different ways to show the same amount.

That was interesting, being able to count the coins that have different combinations.

Let's try some more like that.

Mia has some coins.

What are the names of the coins that she has?

And what are the value?

We can see here that the names of the coins that she has is nickels and she has pennies.

Remember, our nickels are worth 5 cents and our pennies are worth 1 cent.

So let's go ahead and count that.

I'm gonna count our 5 cents first.

Five, 10, 15, count by ones now.

16, 17.

It looks like Mia has 17 cents.

How was this different than counting coins that were all the same?

Did you notice anything that I did differently as I counted those coins instead of the ones that we counted that were all the same?

Let's see what Laila and Nora think about this.

Laila says, "Instead of touching and skip counting "to get the value, I had to slow down to look at the coins."

Our friend Nora says, "I started with the nickels "and counted by five, then I stopped "to start counting by ones for the pennies."

Did you notice how I did that?

Why did I do that?

Let's take a look at another set of coins and see how we can apply this to see if this makes sense.

Our friend, Andre has this set of coins.

What are the name of his coins?

Does he have nickels, dimes or pennies?

What is the value of his coins?

Here, I see that he has pennies and he has dimes.

Dimes are worth 10 cents, and our pennies are worth one.

If we were to apply what Nora was saying, if we start with one, two, and then add 10, I see what Nora's talking about.

That seems kind of hard to start counting by ones and then switch to counting by tens.

Let's see if we can count by tens first and then switch to ones.

So I'm gonna start here and count the dime, 10, 20, stop 'cause we're switching the value of the coins and we need to count by ones.

21, 22, 23, 24, 25, 26 cents.

The value of Andre's coins were 26 cents.

Now let's check out Clare's coins.

I noticed that she only has dimes and nickels.

Let's take a look at it here.

Watch closely as I count these, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55.

I think that there's 55 cents.

Did you agree with the answer that I came up with, and the way that I was skip counting?

Let's see what Nora and Laila think.

Laila says, "I disagree with her answer "because when I counted, I got 75 cents."

Our friend Nora says, "I think you should count the dimes first "because they're worth more, then switch to the nickels.

"That way you don't get messed up while you're counting."

Did you see that same error that Nora and Laila saw?

It's kind of hard in second grade when you see all the coins, one color, 'cause your brain has to stop and kind of think about where you're going.

When I counted, I said 10, 15, and then I continued counting by fives and got 55 cents.

But we know that isn't correct.

Let's do Nora's idea and count the dimes first, and then the nickels.

10, 20, 30, 40, 50.

Now stop and think, we're at 50.

We now have to start counting by fives.

55, 60, 65, 70, 75.

Leo was right, the total of Clare's coins is 75 cents.

Let's check out this set of coins.

I can see three different coins, dimes, nickels and pennies.

How should we count these?

Our friend Laila says, "I think I would start with the dimes then the nickels, "and then the pennies."

We've talked a lot about this idea by starting off with the coins that have a larger value.

It's a little bit easier to skip count.

Let's give it a try.

I'm gonna start off first with my dimes, 10, 20, 30.

Stop for a minute 'cause we have to switch from counting by tens to now skip counting by fives.

We were at 30.

35, 40, 45, 50.

Stop skip counting by fives, and switch to counting by ones.

We were at at 50.

50, 51, 52, 53, 54, 55, 56 cents.

Great job, second grade math mights on counting all of those coins.

Remember, slowing down will help you to be successful when you're skip counting by tens, fives and one.

Now it's your turn to play coin compare level one.

You'll be able to apply what we learned in today's show.

Second grade math mights, thanks for hanging out with me today.

I've had so much fun learning about coins.

We'll see you soon.

(upbeat music) - [Narrator] SIS4teachers.org, changing the way you think about math.

- [Narrator] The Michigan learning channel is made possible with funding from the Michigan Department of Education, the State of Michigan, and by viewers like you.

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