(upbeat music) - [Children] Math Mights.

- Welcome Second Grade Math Mights My name's Mrs. McCartney and I'm so excited that you've joined us today to learn more about math.

Today we're gonna do a number talk together and then we're gonna be working on finding the difference between numbers.

Let's start off first with warming up our math brain with a number talk.

You remember what a number talk looks like?

Let's see which math might is going to help us with our number talk today.

(upbeat music) It's our friend Value Pack.

Value Pack uses a strategy called partial sums.

They like to decompose by place value.

When the Value Pack is clicked together they show the value of what they are together.

When they click apart or separate their value is displayed on their belly.

This is a really great way to help second graders to be able to add using partial sum.

Let's check out our problem that we have for today.

Value Pack wants us to solve the problem 64 plus 35.

Remember there's no using any pencil and paper.

We want you to think about that mentally and think about how Value Pack might want you to solve it.

Let's check out to see what our friend Shannon did as she was solving this problem.

She said, I think the answer is 99.

I decomposed 64 into 60 and four.

Then I decomposed 35 into 30 and five.

Next I added the 60 plus 30 and the four plus five to get 99.

Wow, Shannon had a really great idea for solving that problem with Value Pack.

Let's check it out together to make sure you understand how she solved.

Here we have 64 plus 35.

Shannon decided to take the value of 60 and four and separate it or decompose it by place value, by making it 60 and four.

Over here she decided to decompose 35 into 30 and five.

When she went to add, she added her tens first.

60 plus 30, we know equals 90.

Now that we added our tens let's go ahead and add the ones.

Five and four together, we know makes nine.

Therefore, 90 plus nine equals 99.

Great strategies Shannon thinking of how to use the Value Pack to add the tens and tens and then the ones and ones.

Did you solve it that way?

Let's check out our I Can Statement for today.

Our I Can Statement is I can find the difference between numbers.

Let's check out the way these two students solved this problem.

Jada and Andre found the value of 375 minus 24 in two different ways.

What do you wonder and what do you notice?

Let's see what our friends, Shannon and Kathleen, thought of how they solve the problem.

Shannon notices that Jana and Andre both found the value of 375 minus 24, but thought about it a little differently.

Kathleen notices that Jada used a base 10 diagram and Andre used a number line.

Kathleen and Shannon, those were really great notices.

Let's see now what they wonder.

Shannon says, "are there other ways you can solve this problem?"

Kathleen says, "I wonder about Andre counting back on the number line, could you count up?"

These are both really great wonders to have about the way they solved the subtraction problems.

Let's take a closer look to see exactly how they did this.

Andre decided to solve it using the number line, looking at 375 and wanting to take away 24.

He thought it was easier to start off with a friendly chunk to get rid of that 24.

So he subtracted 375 minus the first 20 and landed on 355.

Now he has to subtract the ones from hopping from 355 back four, which would land him on 351, which is the answer.

375 minus the 24 equals 351.

That's a really great way to be able to subtract in the chunks by taking the second number and hopping back on the number line.

Gina solved it a different way.

She built the mini one, the first number with base 10 blocks, 100, 200, 300, 70, five and then she took away 24, 10, 20 and then the four to show that she was left with 351.

That was great to look at two different ways to do subtraction with base 10 blocks or using a number line to count up or to count back.

Let's do some more of that number line work with our friend Springling.

Hey, Springling, can you come help us out.

Her she is.

You remember Springling.

She has fancy eyelashes and fluffy fur and she was born with a big coily tail.

She loves to hop up or back on the number line.

So you wanna be able to show both of those different ways while we're subtracting.

Let's check out this problem to see if we can solve it the way Springling might.

It says, can you find the value of 189 minus 73?

I have that written here and I'm gonna first start off by counting up to see if I can figure out the distance between 73 and 189.

I'm going to go ahead and try to hop on friendly numbers.

If I'm at 73, what would be a friendly number we could hop to ?

There are lots of options that we could do here, even if you want it to hop a whole 100 if you wanted to go up really high.

Let's try that and just see where we end up.

If I was at 73 and I hopped up 100 all the way to 173, I could tell Springling to hop, Springling hop.

The distance between 73 and 173, we know is 100.

Now that we're at 173, where should we go next?

What happens if I hopped on a friendly chunk but I didn't necessarily go to a decade number, could I still keep going?

If I was at one 173 and I wanted to stop maybe at 179, how far is that?

That let's hop, Springling hop.

We know from 173 to 179 is six.

From 179 to 189, we know is 10.

If we add up Springling's hops we know 100 plus 10 plus six is 116.

We did a great job solving that using the open number line by counting up.

Remember with Springling, you can count up or back to find the difference between the two numbers or the distance.

Andre had a different way of solving using a number line that I wanna check out with this problem.

I'm gonna go ahead and write the number line but I'm gonna stop the number line at the 189 and see if we can hop back 73.

If I was at 189 and I first wanted to hop back the 70 I know that I could hop 70 here and I would end up landing on 119.

Now I need to take away three more.

So if I hopped and took away three more I know that I would land at 116.

So here's where we're finding the answer and we took away the 73 to figure out where we landed.

We just looked at looking at the number lines two different ways with subtracting.

The one we looked at the distance between the two numbers and we counted up on the number line.

The other one we started with that minuend at the end and we took away the subtrahend.

Both really great ways to solve with subtraction.

Maybe you should use one of the strategies sometimes and the other strategies on other times.

Let's check out this problem to see what your thoughts are.

Can you find the value of 647 minus 46?

If we started off at 46 and we tried to figure out the distance between 46 and 647.

Or do you think it's better for us to start at 647 and subtract the 46?

I wonder which one will be more efficient.

Do you think we should count up or back on the number line or should we start with that minuend and hop back in the chunks by subtracting it off on the number line?

Let's test it out to see which one takes us longer or shorter.

Let's take a look at this one first.

We have the 46 and wanna find the distance between 46 and 647.

I could hop from 46 up one to 47.

Hop Springling hop.

We know that's only one.

Now I could hop, I know it sounds crazy all the way up to 647 because that is 600.

When I add that together the distance between 46 and 647 is 601.

Let's try now by taking the total and then subtracting the tens and the ones off using the number line.

Here we have the number line ending at 647.

We wanna take away 46.

Let's start off first with taking away the 40.

We're gonna hop back 40 which we know would land us at 607.

Now we need to take off six.

If we hop back six, that would land us at 601 which is the same answer that we got here.

647 minus 46 equals 601.

When you look at both of those strategies did you like one better than the other?

I know some second graders have a hard time counting back but it's up to you.

Whatever strategy works best for you is the one that you should use especially if you can explain how you solved it.

What is Springling doing?

She is playing in the paint and is making splotches on problems.

Springling wants us to use our thinking to help figure out where the answer should be where the big paint splotch is.

Let's check out this first problem to see if we can make Springling proud.

Our first problem that we have is 900 minus 370 equal splat.

We don't even know what the answer is.

Let's check it out on the whiteboard to see if we can solve it the way Springling might want us to.

Here we have 900 minus 370.

We made an open number line where we're looking at the distance between 370 and 900.

Springling likes to make really big hops to keep her fur very fluffy.

So where would she have if she started at 370 and she was looking for a friendly number?

I think I know.

This is really close to 400.

Hop Springling hop.

We know that that was 30.

Do you think you could go from 400 all the way to 900?

I definitely think you can.

Hop Springling hop.

When we do that, we know the distance is 500.

Now we can add 30 plus 500 to get 530.

Great job using Springling on that open number line.

Do you think that we can use Springling when there's an addition missing add in problem?

Let's check out this problem.

250 plus splat equals 1,000.

How could we use Springling to help us figure out what is on the splat?

When we're using missing add in, an easy way to figure out that missing add in is to subtract.

Let's check it out here.

We have 250 plus blank equals 1000.

If I want to figure out what this other number was we could figure out the distance.

So let's put 1000 here and 250.

It's same idea if I did 1000 minus 250 it's gonna tell us what this other part is.

You also could count up to figure out how we got to 1000.

Let's check it out here.

I might start here at 250, hop to a friendly number, which is 300, which I know that that is 50.

If you wanted to, you could go all the way from 300 up to 1000, which we know that is 700.

Now, if we add the 700 plus the 50 we know that that missing number is 750 because 250 plus 750 equals 1000.

What?

Springling can help us with missing add in too?

Knowing what we're doing with the different operations of looking at that total distance can really help us to solve multiple problems in math.

Now it's your turn to find the difference between numbers with Springling.

We're gonna give you four problems similar to what we did today to see if you can use the strategies we've talked about.

Thanks Second Grade Math Mights for a great session together.

We ended up doing a number talk earlier with Value Pack and then we learned a lot about how we can use subtraction for addition with missing add in and just regular subtracting with Springling.

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

(upbeat music) - [Child] Sis4teachers.org.

(upbeat music) - [Girl] changing the way you think about math.

- [Announcer] The Michigan Learning Channel is made possible with funding from the Michigan Department of Education, the state of Michigan, and by viewers like you.

(upbeat music)