(playful music) - [Children] Math Mights.

- Welcome 2nd grade Math Mights.

My name is Mrs. McCartney.

Thanks so much for joining 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 going to read, write and tell time.

Let's start off first by warming up our math brain with our mystery math mistake with our friends the Math Mights.

Oh, no, what has happened to all of our friends.

It looks like Abracus is holding on to T-Pops cane.

Wait a minute, all of our Math Mights have all their strategies mixed up.

The way the mystery math mistake works is we're going to have a character that has told me how to solve a problem.

You're gonna put on your magnifying glass to see if you can find the mystery math mistake as I'm going through it.

This will be an idea that you have already learned about, so be sure you look really carefully to see how our friend solves it.

Look at our friends Springling, she's upside down and all confused.

She's trying to solve 97 minus 48.

She starts off her open number line trying to find the distance between 48 and 97.

She told me she really likes to hop to friendly numbers.

So she wanted to stop at 50.

The distance between 48 and 50 we know is two.

Then she wanted to go from the 50, and instead of stopping at each decade, she went ahead and stopped at the number 90.

The distance between 50 and 90, we know is 40.

Then she hopped the last distance from 90 to 97.

When she added up 40 plus seven plus two, she got 48.

97 minus 48 is 48.

What do you think about the way Springling solved that problem?

Did she mess up at all or did she do it A okay?

Let's see what our friends think.

Rich said, when I added 48 plus 48 to check the problem, it didn't equal 97.

Let's take a look to see what Rich is saying.

He decided to look at the 48 and the 48.

When you do a subtraction problem, you can check it by doing the inverse operation.

By taking the subtrahend and the difference and adding it together to see if you get the minuend.

If I were to add together 48 plus 48, I can solve it to see if the total is 97.

If I add my 40 plus my 40, I know that that equals 80.

If I add my eight plus my eight, I know that that equals 16.

Oh, Rich is right.

The total ends up being 96, not 97.

That's a great indication that we solved something wrong along the way.

But what part did we solve incorrectly?

Let's see what our friend Kim says.

Kim said it looks like you added incorrectly.

If I add the distance of two plus 40 plus seven, it equals 49, not 48.

Boys and girls, did you discover that same mistake that Springling made?

Let's check it out.

We're going to look over here, 40 plus seven plus two 40, 47, 48, 49.

We have a mystery math mistake that we have discovered.

We now know that 97 minus 48 equals 49.

Springling is feeling much better that you were able to help her, she's no longer upside down and confused.

Great job solving that mystery math mistake.

Let's check out our I can statement for today.

The I can statement says, "I can tell time read, and write time using a.m. or p.m." Let's take a look at this clock.

What do you notice?

What do you wonder?

I noticed a lot of numbers on that clock and I also spotted a number line.

Let's see what our friend Rich and Kim think.

Rich said, I noticed the same numbers are on the number line and the clock.

There are no hands on the clock.

Let's check out to see what Rich noticed.

As I'm looking at my number line, he's seeing the same numbers.

Five, 10, 15, 20, and so on.

I also see that on the number line, and the clock.

Let's see what Kim thinks.

He says, there's a lot of little tick marks between the numbers.

Let's see what he means.

I do notice that as well.

As I'm looking at the clock, I see a bunch of little tick marks in between.

When I look at the number line, I also see tick marks in between.

Let's see what they wonder.

Rich wonders why there are numbers on the outside of the clock.

Kim wonders why are the numbers counting by fives?

Why is the five written with a zero in front of it?

If we look, I do see all of these other numbers outside the clock.

We talked before about seeing the inside numbers, and then I think Kim has a really good point of looking at why does this five have a zero in front of it.

Those were really great notices and wonders.

I want you to think about the clock and the number line that you saw.

What is the same and different about the images that you see.

When we look over here we can see that they are the same because they're both counting by fives.

They are different in the way the zero and the five are represented like Kim said.

On the clock it says 05, and on the number line it says five.

The numbers around the clock show how we would write it in a digital time.

So if we were to see one, we would see a colon and then 05.

Great job on using your thinking with the clock and the number line.

Let's take a look at this clock.

What are two ways to read the time on the clock?

What are you thinking?

I know we could just tell the time, but let's see what Kim and Rich think.

Kim says it's 4:30.

The hour hand is between the four and the five and I counted by five to get to 30.

Let's take a look to see what Kim is talking about.

He is correct.

Like we talked about before the hour hand is between the four and the five.

As he went around the clock he counted 5, 10, 15, 20, 25, 30, that's why this shows 4:30.

Let's see what Rich thinks.

Rich said it's half past four, I can tell because the minute hand has moved half way around the clock.

Remember, if we have it all the way at four o'clock where it's starting the hour.

If we move it this half way, we can also say the time that it's half past four.

As you look at that our hand it's kinda nice 'cause it is past the four.

Great job looking at how we can say time in two different ways.

Let's check out another one.

What are two ways to read the time on this clock?

Do you have any ideas of different ways that you could tell the time?

Let's see what our friend Rich and Kim think.

Kim says, it's 4:15, the hour hand is by the four.

I counted by five to get to 15.

He's seeing that the hour hand is definitely still by that four, and what he said is he counted from four o'clock by fives to get to 15.

5, 10, 15, so it is 4:15.

If you get stuck you can see on the clock that you remember to skip count by fives.

Our friend Rich says it's quarter past four.

I can tell because the minute hand has moved one quarter.

Remember if we think about our clock being divided like we did with fractions into four equal parts, this section here represents one quarter, and he is right.

We are a quarter past the hour of four.

2nd grade Math Mights you're really getting the hang of this.

All right, I'm gonna make it trickier, are you ready?

Take a look at this clock, what time is shown on the clock.

Don't get tripped as we look at the hour hand, let's take a closer look.

If I look at this, I want you to think of even taking a line to see is it really at eight.

If you look carefully, it's not quite completely on the eight.

So don't get tricked that this is in the hour of eight o'clock.

We still are on our way, in the seven o'clock hour.

If I go around the clock, we know it's 7, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50.

So it's 7:50.

If we wanted to do that in digital time, we're gonna put the colon in between.

We know that it is seven, and we know that our minute hand is pointing towards the 50.

So it is 7:50.

Excellent job.

Let's try another clock.

Let's take a look at this clock.

What time is shown?

If I look here, this one's a little bit easier because the hour hand is right on the three.

When I go to look at the minutes here, should I just write five?

Well, that looks kinda funny.

Three, five, we know it's not 3:50.

Remember, we talked about earlier why that clock we looked at at first said 05?

This is exactly why.

Because if we're looking at the digital time, we wanna say that it is 3:05.

All right, I have one last one for you to check out.

It's really tricky, So make sure you look carefully.

Take a look at this clock.

What time do you think it is?

Some students right away say that's easy, it's 1:55.

Do you agree with that based on all the things that we've talked about with time.

if I look carefully at this hour hand, and I try to draw an imaginary line, it is not quite to the one.

So we are still in the hour of 12.

So it is 12 for the hour and 55 for the minutes.

If you've noticed all the times we've talked about have not been talking about whether or not we're looking at the morning, or we're looking at the afternoon.

Let's look at how we would label that with a clock.

What are some things you're doing in the a.m. Let's first talk about what a.m. means.

a.m. stands for ante meridiem this means before midday or before noon.

The a.m. time period is 12 hours from midnight until noon.

12 a.m. is the start of a new day.

If you were to think about activities that you might do in the a.m. maybe waking up in the morning, and brushing your teeth, and maybe getting dressed and having breakfast.

Those things would happen in the a.m.

If we look at what p.m. stands for, we know that it means post meridiem.

This means after midday or afternoon.

The p.m. time is 12 hours from noon to midnight.

12 p.m. starts the second half of the day.

What are things that you would do in the p.m. You might be doing your homework, or waiting to eat a meal, or maybe getting ready to get in your pajamas to go to bed.

Let's take a look at these activities.

Do you think you can figure out which ones are happening in the a.m. or in the p.m?

If I were to start to think about 7:30 a.m. or p.m., which thing would I be doing?

I think at 7:30 I might be eating breakfast in the morning.

So I'm gonna put an a.m. next to it and match it up to eating breakfast.

At four o'clock, I would probably not yet be doing my homework and I wouldn't be in bed sleeping or eating lunch.

But if it was four o'clock p.m., I might just be getting home from school.

At 12:05 If it was a.m., I would probably for sure be asleep.

But if I looked at 12:05 p.m. it might be time for me to eat lunch.

At eight o'clock in the morning, I might be already on my way to school.

But at eight o'clock p.m., I might be in bed sleeping.

That leaves us at 4:35 to do our homework.

We're not gonna do that in the a.m.

So we're gonna match that with p.m, and put that for when we do our homework.

Great job matching up the activities to a.m. and p.m. Now it's your turn to tell time using a.m. and p.m. like we did today.

2nd grade Math Mights, I've had a great time hanging out with you today, starting off helping Springling with her strategy as she was all confused.

And then we had so much fun with talking about time and being able to tell it on our analog clock and the digital clock.

I sure hope that you'll join us again for another Math Might show soon.

(mellow music) (playful music) - [Boy] Sis4teachers.org, - [Girl] changing the way you think about math.

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