Math Mights | Measuring with Centimeters | Season 2 | Episode 203

(soft music) - [Kids] Math Mights!

- Welcome, second grade Math Mights.

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

My name is Mrs. McCartney, and we have a great show planned for you.

Let's check out our plan for today.

Today, we're gonna be doing a mystery math mistake, and then we're going to be measuring with centimeters.

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

Oh no, look at all of our Math Mights.

What has happened?

They got stuck in a cyclone, and all of their strategies are confused.

Our friend D.C. is holding Abracus' wand.

What is going on?

Wow, here's how the mystery math mistake works.

One of the Math Mights friends has shared a strategy with us, but somewhere along the lines, they are messed up in their strategy.

It's your job to use a magnifying glass to look closely to see if you can figure out where the mystery math mistake is, so that we can help set our Math Might friends straight.

Let's see what Math Might might need our help today.

It looks like it's our friend, Abracus.

He's trying to solve 19 plus 21, and he thinks that it equals 41.

He decided to take that 19, and change it to a 20, and keep the 21 a 21 to get 41.

Wow, did you see the mystery math mistake that Abracus has done?

It might be a little bit hard to see it on the screen, so let's work it out together, so we can really see what Abracus was thinking.

Here I have the problem 19 plus 21.

Abracus, I think was trying to make that 19 a friendly number by adding one, and making it 20.

And then he decided to take the 21, and take away one to make that friendly number a 21.

He then added the 20 and the 21 together to get 41.

Did you take a closer look to see what that mystery math mistake might be?

Have you figured out how we can help our friend Abracus?

Let's see what some of our friends are thinking.

One of our friends, Stacey, says, I think that Abracus was trying to make the 19 into a 20, and the 21 into a 20 to make it easier to add.

Do you understand what Stacey's pointing out?

Let's take a look.

She did say that Abracus was trying to take that 19, and make it a 20 to make it easier to add.

And over here, Stacey thinks that Abracus meant to make the 21 a 20 to add it a little bit easier.

Do you agree with that mistake?

Let's see what our friend Neil is thinking.

Neil says, I agree with Stacey.

I think he forgot to take away one from the 21 to make it a 20.

So the answer should be 20 plus 20 equals 40.

Ooh, he has a really good point.

Let's check it out to see if we can help fix the mystery math mistake.

Over here, if we took 21, and we took a one, it wouldn't still be 21.

We know that this and the correction should be a zero, and 20 plus 20 does not equal 41.

We know it equals 40.

Our friend Abracus uses a strategy called compensation, and in this particular problem, he made a change by adding one, and taking away one to make the problem a lot easier.

20 plus 20.

You did a great job helping set Abracus straight to help find that mystery math mistake.

When second graders can find mistakes in math, we know that you're using that mathematical thinking to find errors, and explain your thinking.

Awesome job.

Let's check out now our I Can statement of the day.

Our I Can statement says I can measure with centimeters.

Today, we're gonna be learning a whole lot about centimeters.

I want you to think about, what do you remember from first grade from centimeters?

Did we talk about measuring with centimeters in first grade?

A lot of times in first grade, we're using different measurement tools, like our Unifix Cubes, or maybe even paper clips.

Let's come back and see what some of my friends are thinking about as to far as what they know about centimeters.

Our first friend says, as he's thinking about measurement, he knows that measurement has to do with finding out how long something is.

That is a great point.

In order to measure something, we have to figure out the length of something.

That's a great point.

Let's see what our other friends want to add.

Our next friend says that when we're thinking about measurement, she's thinking about how you can measure with a ruler.

We know that you can measure with a ruler by being able to line up that ruler to measure, or having that starting point.

Our next friend is really excited to share her thinking.

She said, you can measure with other objects.

That's true, you can use a ruler.

You can use it in centimeters or inches, or even measure with different tools as a standard measurement of units.

Our last friend thinks for measurement that we can measure your weight in pounds.

That's right, or even ounces when we're looking at food.

Today in our show, we're gonna be focusing on centimeters.

I want you to take a look at Priya's iguana we're gonna try to measure.

Priya measured her iguana with a string.

Let's see how long it is.

We're gonna fill in that sentence stem that says Priya's iguana is hm straws long.

One of our friends, Stacey, went ahead and took the string, and she measured it with straws, and it was four straws long.

Our friend Neil decided to measure the string of Priya's iguana, and he measured it with centimeter cubes, and figured out it was 40 centimeters long.

Let's take a look at the string that was the length of Priya's iguana.

The length of the iguana is from the beginning and end of this string.

That's a pretty big iguana, don't you think?

When we look at measuring it with straws, our friend Stacey was using these straws to measure it.

When we're measuring with an object, just like you learned in first grade, we're going to measure it from end point to end point to make sure that that straw lines up for the actual length of it.

So here I can see Stacey is correct that there were four straws that were measuring the length of this string.

Now our friend Neil said something like it was 40 centimeters.

How would you know that what we're looking at here is 40 centimeters?

That brings us to really talking about first, what is a centimeter?

One great tool that we use in our grade, in second grade, is to be able to use centimeter cubes.

These look a lot like our base 10 blocks that we're using.

If the length of one edge of the centimeter cube is one centimeter, how long is one block?

So here I have kind of our one base 10 block, and then we kind of have our longer one.

So if this, if they're measuring, if Neil went and measured the string that measured Priya's iguana, he would have to line up each of these to line that up.

That would kind of take a long time.

But if we were to look the length of the centimeter cubes that are put together, which makes up our base 10 block, we could probably measure this faster.

So let's see how many of our one centimeters cubes are in the length of this block.

We can count it.

One, two, three, four, five, six, seven, eight, nine, 10.

This is making a lot more sense as to why Neil would say that the length of the string was 40 centimeters.

Let's test it out to see if we can measure it the same way.

Here I'm gonna line up the centimeter cubes that are set up in 10s, so we can easily skip count by 10s.

10, 20, 30, and 40.

When we look at the length of the string, we can see that it is 40 centimeters long.

That makes a lot of sense, thinking about how in second grade, maybe if you don't even have a ruler, that we can start to understand how to measure centimeters.

Who would have thought our base 10 blocks also are known as centimeter cubes?

This would be great for us to measure with today.

Let's see what we're gonna measure.

I want to see if we can measure reptiles in centimeters.

I have four different reptiles that we're gonna work on measuring together.

Look at this tiny dwarf gecko.

Do you have an estimate thinking of our centimeter cubes?

How long is that dwarf gecko?

It can't be very long.

Let's test it out.

I have our centimeter cubes here, and I'm gonna line up from end point to end point to see how large our tiny, tiny gecko is.

When I line this up, I can see that he is two centimeters long.

Let's try out now our next creature over here, which is known as a blue tongue skink.

This has a starting point and a end point.

Now it's a little hard when you're measuring reptiles, or measuring things that aren't just perfectly linear.

So under these pictures, we actually kind of measured with a line going from the front to the back.

And so this is sort of that start point, and here's that end point.

And if we kind of go up, I know that it's the full length of this particular creature.

I'm gonna start putting different centimeter cubes here, and measuring one at a time.

Based on what we talked about a few minutes ago, do you think there's a more efficient way with centimeter cubes talking about the tools that we have to measure this?

I hope that your thinking that we can use our row of our base 10 block to measure this a little bit quicker.

Let's try that out.

I'm gonna move these centimeter cubes, and try to do our whole row of 10.

This is a lot easier for me to line up without things kind of going all different ways.

Hey, look at that.

This particular blue tongue skink is exactly 20 centimeters long.

And I know that because I can skip count by 10s, 10, 20.

Let's take a look at our next reptile that we're going to measure.

Here, I have a musk turtle.

Again, you see the points on the line underneath that are from each end point to measure.

I know it's gonna be a better idea for me to go ahead and use the 10 that's already together.

When I'm looking, there's a little bit of space left for me to put another cube here, and I can see that that one is 10, and one more, so our musk turtle is 11 centimeters long.

We have one more reptile, a kind of a snake.

Let's take a look at it, and see.

Here, we have a ring neck snake.

Again, you see the end point to end point.

I'm gonna go ahead and use those base 10 blocks to measure, to see how long it is.

It looks like it's going to be a little bit longer than just the 20.

I'm not quite to the end, so I'm gonna keep going with two more.

If we have 10, 10, and two, how many centimeters long is our snake?

We can count it.

10, 20, 21, and 22.

Now we've measured each of our reptiles with using our centimeter cubes to figure out how long they are.

I wonder if we can answer some math application problems to go along with our measurement.

Here I have our blue tongue skink and our musk turtle.

The question is asking how much longer is the blue tongue skink compared to the musk turtle?

What's a way that you know that we could solve this problem?

One of the ways we could do is kind of look at the total of both of them, and we might be able to apply a little bit of math.

Here I have our blue tongue skink and the musk turtle.

One way we could do this is to try to figure out the length, and compare the how much longer one is from the other.

I'm gonna go ahead and do a visual model.

This is going to be for my skink, and this is going to be for my turtle.

I'm gonna go ahead and make a longer bar here, and I know we talked about that this is 20 centimeters.

So I'm gonna label that 20 centimeters.

This one here, the musk turtle, we know is 11 centimeters.

So I need to make sure that the second bar that I'm building is going to be shorter than the top.

So here I have my 11 centimeters.

Our question here is asking, how much longer is the skink from the turtle?

And so the way we could solve that is many different ways.

The way that problem would look would be 20, we can even think of it as a number bond, 11.

What's the other part that goes with it?

We know that if we did nine and 11, that would be one way you could solve it.

Another way you could solve it is doing 20 minus 11, and solving it with nine.

If you weren't able to figure out that subtraction on your own to get the other part, you could always count on, or count up like our friend Springling does.

Great measuring.

Now it's your turn to practice measuring with centimeters.

You're going to get to do exactly what we did today in the show by measuring some of our Math Might friends.

Second grade Math Mights, we've had so much fun from our mystery math mistake to measuring with our newfound centimeters.

I sure hope that you join me for another Math Mights episode soon.

(soft music) - [Kid] Sis4teachers.org.

- [Girl] 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.

(soft music)

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