(playful music) - [Kids] Math Mights!

- Welcome, second-grade Math Mights.

My name is Mrs. McCartney.

Thanks so much for joining us today to have some fun with math.

Let's check out our plan for today.

Today, we're gonna start off with a Mystery Math Mistake, and then we're gonna start to tell time to the half and quarter hour.

Let's start off first by warming up our math brain with a mystery Math Mistake with my friends, the Math Mights.

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

It looks like they're all dizzy and confused with their strategies.

The way Mystery Math Mistake works is I'm going to give you a concept that you should be familiar with as a second-grader.

You're gonna put on your magnifying glass to see if you can discover where one of our characters makes a mistake.

Be sure that you can explain your reasoning to someone.

Let's check out to see who we have.

Today we have our friend Springling.

Oh no, she's upside down and all confused.

She helped tell me how she solved 82 minus 37.

I'm gonna show you how Springling told me.

And I wanna see if you can find her Mystery Math Mistake.

She wanted to find the distance between 37 and 82, so she put it on the open number line.

She said, "I know if I'm at 37, if I wanna get to the next friendly number, it's going to be 40."

So Springling made a hop and kept track that she went three.

As she started going along, she says, "I don't need to stop at 50 and 60 and 70."

She's gonna go all the way to 80.

Hops, Springling, hop.

She knew the distance between 40 and 80 was 30.

Then she knew all she had to go was from 80 to 82, which is two.

She added up the numbers that she hopped.

30 plus three is 33, 34, 35.

So Springling said, "82 minus 37 equals 35."

Did you find the Mystery Math Mistake that our friend Springling made?

Or did she do the problem perfectly?

Let's check out to see what our friends think.

Our friend Rich said, "When I added 35 plus 37 to check the problem, it didn't equal 82."

Boys and girls, what does Rich mean by the comment that he made?

Let's take a look.

He likes to do the inverse operation by adding to see if he still gets the same total that we started with.

So he said, if he added 37 plus 35, it doesn't equal 82.

Well, let's see.

We know 30 plus 30 is going to give us 60.

If we added our seven and our five, we know that that's going to give us 12.

So what Rich is saying is this total actually equals 72.

If we were to do the inverse operation, it should equal this original menu add that we had.

I think Rich is onto something here about the way that Springling solved that problem.

Let's see what our friend Kim thinks.

He said, "It looks like you added the distance wrong between 40 and 80.

That would be 40, not 30.

So the answer should be 45."

Let's go back and take a look here.

He is saying the distance between 40 and 80, uh-oh, I see it right here.

The distance between 40 and 80 is 40, not 30.

So if we go to add up the hops, 40 plus two plus three would give us four 45, not 35.

Did you find that Mystery Math Mistake?

By discovering mistakes in math, you're becoming a strong mathematician.

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

I can tell time with halves and quarters.

I want you to take a look at these two clocks.

What do you know about ways to tell time?

What words do you use to talk about time?

Have you seen different clocks maybe at school or at your house?

These two clocks look different.

Let's see what some of our friends think.

When we look at telling time, one of our friends says, "Clocks measure and show time."

We measure time in hours and in minutes.

Let's see what our next friend is bringing to the table.

He says, "Some clocks are a circle with one through 12 around it.

They show time with an hour hand and a minute hand."

Here we have a clock like he is describing.

You can see the numbers from one all the way to 12, and you see the hour hand and the minute hand.

Let's see what else our friends have discovered.

Someone said that some clocks just show numbers.

Have you seen a clock that only shows numbers?

That is called a digital clock.

Let's see what else someone else has to say.

You can say, o'clock when it's a new hour, like three o'clock.

That's a great word to describe time, o'clock.

You've heard someone say four o'clock, five o'clock, six o'clock, right?

Let's check out what else our friends know about time.

You must say half past when it's 30 minutes after the hour, like 3:30 is half past three.

Wow, a lot of our friends know a lot of information already about clocks.

Did you already know some of the things that were on our list about telling time?

We're gonna talk more about this today.

Take a look at these two clocks.

Why don't both clocks say four o'clock?

Well, that's a really good question.

When I'm looking at 'em, they kind of look the same.

I wonder what our friends have to say.

Rich says, "The clock on the left doesn't show four o'clock because the hour hand is pointing to the 12 and the minute hand is pointing to the four.

Let's take a look on my clock to make sense of what Rich is saying.

Rich says that this is not showing four o'clock.

The red hand, or the short hand, is our hour hand.

The longer hand, or in this case, the blue, is the minute hand.

Our minute hand is pointing towards the four and our hour hand is pointing towards the 12.

So this does not show four o'clock.

Let's compare that to the other clock that we saw.

On my clock, I went ahead and put the hour hand pointing towards the four, and the minute hand pointing towards the 12.

Did that make sense on how to show if it's saying o'clock?

Let's take a look now to see a clock a different way.

Which clock shows half past?

Why doesn't the other one show half past?

Well, these clocks look a lot of like, in fact, I can see the minute hand is pointing towards the six, which is halfway around the clock.

Let's see what our friend Kim has to say.

He said, "The clock on the right does not show the 7:30 because the hour hand is supposed to be between the seven and the eight.

Let's take a look at my clock to see exactly what Kim is thinking.

I reset the clock right now at seven o'clock, because we want to be able to show half past.

If I thought about what I know about fractions, if I wanted to divide this clock in half, I know that I have to bring that minute hand down to the six.

I want you to pay close attention to what's happening to the hour hand as it moves through the clock.

I'm gonna move the minute hand going down.

What do you notice is happening to our hour hand?

As the time is moving, our hour hand now is half way between seven and eight.

This helps us know that it's 7:30.

If the hour hand is right on the seven, that would not read 7:30, because the only time it's smack on the seven is when we're up at o'clock.

As I start to move it around the clock, you can see that the hour hand is moving.

This is a really important skill in second grade, especially as you start to draw clocks.

Remember, as you're going around the clock halfway, that hour hand is slowly moving towards the next hour.

The next one we're gonna do makes it a little bit more tough.

Let's check it out.

Draw in the hands to show 1:30.

If we wanna put in 1:30, we wanna look at where that minute hand is going to go first.

As I start going around the clock, we can skip count by fives: five, 10, 15, 20, 25, 30.

You see that it's halfway.

So I'm gonna make the longer hand point down to the six because that is at the 30 mark or half way.

Now, when I go to put it in one, do I want to put that right at one o'clock?

Remember, on the clock that I was showing you, as I was moving that minute hand, the hour hand is moving as well.

So, I'm gonna choose to put my hour hand halfway between one and two.

This will represent that my hour is in between one and two.

Don't think that it's 2:30 'cause it hasn't yet gotten to the two yet.

So it's kind of halfway.

So this would read 1:30.

Great job remembering where that hour hand is.

That's always tricky in second grade.

Let's take a look at these clocks, fractions and words.

Do you think you can find the matches for the sets of cards?

Let's check out to see what our friend Rich thinks.

Rich says, "I think that A, H, and I go together, because they all show quarter til the hour.

There is only one quarter left to complete the hour."

Let's take a look.

This word says quarter till.

What does that mean?

Quarter til, if we look here, we see that three quarters or 3/4 is shaded.

There's only 1/4, or one quarter, until it's completely full.

It's the same thing as you look at a clock.

If you're looking at the minute hand, you can see that a quarter of it is passed.

I'm gonna kind of draw a line here.

You have this quarter has passed.

This quarter has passed.

This quarter on the clock is passed.

So we only have a quarter till we get to the next hour.

Great discovery, Rich, looking at those different pieces of the words, the fraction, and the time to make sense of that.

Our friend Kim decided to look at all of those cards, and he thinks that B, G, and L go together because they all show half past the hour.

There's only one half left to complete the whole.

Let's take a look.

Here is the word half past.

What does that mean?

Half past means that half of it has gone past.

If we look at it like we thought about on fractions, we have these two halves.

We have one half shaded.

The other half is not shaded.

If you apply that understanding to clocks, when we look at it this way, we can see that the minute hand is half past and it only has halfway to go.

But if we look at that term half past, if we shaded this in, we can see that half of the time has passed.

So this is a great terminology to look at how far has passed versus the other one where we said quarter till the next hour.

Are you understanding that language?

When it says quarter till, it means how much is left until the next hour.

When you hear the word past, it means that it started at the hour and has moved past.

Let's check out one more term.

This one says quarter past.

Our last term said quarter till.

We know if we look at this whole with our fractions, we can see that one quarter is shaded.

So quarter of it has already passed or been highlighted here.

Same thing if we look at our clock, and I were to divide it just like our fractions, we know that 15 minutes or quarter of our time has already passed.

Excellent time telling, Math Mights.

Now it's your turn to play Time Match-Up.

You're gonna apply what you learned today by matching the words that we talked about with digital and analog clocks.

Math Mights, I've had so much fun hanging out with you today, really helping Springling get back on her spring to figure out how to solve the distance between two numbers the correct way.

And then we did a ton of stuff with learning the beginning parts of how to tell time.

I sure hope that you join us next time.

(bright music) (mellow music) - [Kid] sis4teachers.org.

(air whooshing) - [Kid] Changing the way you think about math.

(bright music) - [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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