Math Antics - Telling Time - Free Educational videos for Students in K-12

Math Antics - Telling Time - By Lumos Learning

Transcript


00:03	uh huh . Hi , I'm Rob . Welcome to
00:07	math antics . In this lesson , it's finally time
00:10	for us to learn about time like distance . Time
00:13	is something you can measure and represent as a number
00:16	, but we use different units to measure time and
00:19	also different devices to make the measurements . There are
00:23	lots of different units of time from really small ones
00:26	, like nanoseconds to really big ones like centuries .
00:29	But in this video , we're only going to learn
00:31	about four of the most common units of time seconds
00:35	, minutes , hours and days . You should be
00:38	really familiar with the day , you know , because
00:40	you encounter one every day . A day is the
00:43	amount of time it takes the Earth to rotate on
00:45	its axis one time . So it's pretty much the
00:48	fundamental unit of time for our planet . But as
00:51	important as the day is , we need smaller units
00:54	of time for planning daily activities , so people decided
00:58	to divide up each day into 24 equal chunks of
01:01	time called hours . Even though an hour is only
01:04	one 24th of a day , it's still a pretty
01:07	long time , so we divide hours up into even
01:10	smaller units called minutes specifically , each hour is divided
01:14	up into 60 minutes . So a minute is 1/60
01:18	of an hour . And to get even smaller units
01:21	of time , we divide up each minute into 60
01:23	equal parts called seconds . So a second is 1/60
01:27	of a minute , going from the smallest to the
01:30	biggest . You should memorize that . 60 seconds equals
01:33	one minute . 60 minutes equals one hour and 24
01:37	hours equals one full day . There are some common
01:40	abbreviations for these units that you should know too .
01:43	D for days . H four hours , men for
01:47	minutes and s for seconds . One of the earliest
01:51	devices for measuring time was called a sun dial .
01:54	It was basically a flat disk with a triangular pointer
01:57	in the middle As the earth rotated , the shadow
02:00	of the pointer would slowly change position and pointed different
02:03	markings on the edge of the circle , which represented
02:05	different times of the day . Are you tired of
02:08	the man telling you what time it is ? Now
02:10	? You can get the time directly from the source
02:13	with the Sun O Matic 3000 . Just put it
02:15	in your yard and let the sun do the rest
02:18	for daytime use only not for use in cloudy conditions
02:21	. Times may not be accurate , depending on latitude
02:24	, some calibration required . The sun dial was a
02:27	really cool invention , but it had a lot of
02:29	limitations . Fortunately , there are much better modern devices
02:33	for keeping track of time . In fact , you
02:35	probably have one hanging on your wall at home or
02:37	in your classroom that looks something like this . This
02:40	traditional clock is designed to keep track of three different
02:44	units of time , seconds , minutes and hours .
02:48	That's why it has three different pointers or hands .
02:51	This thin red pointer is called the second hand because
02:54	it helps us keep track of seconds . This thicker
02:57	black pointer is called the minute hand because it helps
02:59	us keep track of minutes , and the shorter black
03:02	pointer is called the hour hand because it helps us
03:05	keep track of ours . Oh , and the circle
03:07	itself is often referred to as the clock face .
03:11	Oclock is actually kind of complicated , so to see
03:14	how it works , let's start with the version that
03:16	has everything removed except for the second hand and the
03:19	60 marks around the edge of the clock face .
03:21	Why are there 60 marks around the edge you'll see
03:24	in just a minute , starting with the second hand
03:27	, pointing straight up at the top of the clock
03:29	face . If the hand rotates to the right so
03:32	that it's pointing at the next mark , that means
03:34	that one second of time has passed . So we'll
03:37	label that mark one . The next mark will be
03:39	to the next three and so on until we get
03:42	all the way around and the hand is pointing straight
03:45	up again . That means exactly 60 seconds have passed
03:49	. So label that mark with a 60 . But
03:51	we could have labeled that top mark as a zero
03:54	, since that's where the sequence of numbers starts .
03:56	That's one of the cool things about o'clock being a
03:58	circle . The starting point is also the ending point
04:01	. So as soon as you hit the end 60
04:04	seconds , you're also back at the beginning zero seconds
04:08	. The reason that there's exactly 60 marks around the
04:10	edge of a clock is that 60 seconds equals one
04:13	minute . That means when the second hand makes one
04:16	full rotation around the clock face , exactly one minute
04:20	of time has passed , and if it makes two
04:22	full rotations , two minutes of pest and if it
04:25	makes three rotations , three minutes of pest and so
04:28	on . So even though the second hand is counting
04:31	seconds , it also helps us know how many minutes
04:33	have passed . But how are we going to keep
04:35	track of those minutes ? Well , that's where the
04:37	minute hand comes in handy , so let's add it
04:40	back to our simple clock . The minute hand works
04:43	a lot like the second hand . The main difference
04:45	is that it travels slower 60 times slower to be
04:48	exact , since a minute is 60 times longer than
04:52	a second . While the secondhand travels all the way
04:55	around the clock , the minute hand only moves from
04:58	one mark to the next . For example , if
05:01	both hands start straight up at the top of the
05:04	clock , while the secondhand travels all the way around
05:07	the clock , counting out 60 seconds as it goes
05:10	, the minute hand will only travel from 0 to
05:13	1 , because only one minute has passed . Then
05:16	, while the secondhand travels around the clock is second
05:19	time , the minute hand will travel from 1 to
05:22	2 because two minutes have passed notice that we use
05:25	the exact same set of 60 marks to measure both
05:28	seconds and minutes . But the different hands tell you
05:32	how to interpret those marks . If the second hand
05:34	is pointing at the fifth mark , it means five
05:37	seconds . But if the minute hand is pointing at
05:39	the fifth mark , it means five minutes . Of
05:42	course , being able to quickly tell which market hand
05:44	is pointing at is tricky , since clocks don't usually
05:48	number every mark . So to make it easier ,
05:50	the inventors of the clock decided to make every fifth
05:53	mark bigger or bolder , so you could skip count
05:56	by fives , which helps you quickly tell where the
05:58	hands are pointing . For example , if the second
06:01	hand is pointing right here , you can tell right
06:04	away that it's just two marks passed the 15th mark
06:07	. So it's pointing at 17 seconds since 15 plus
06:10	two equals 17 . And if the minute hand is
06:13	pointing here , you'll quickly see that it's just two
06:16	marks before the 40th mark . So it's pointing to
06:19	38 minutes since 40 minus two equals 38 . These
06:23	bigger marks are so helpful for reading a clock that
06:26	you should memorize the values they represent when the minute
06:29	or second hands are pointing at , especially the ones
06:32	that break the clock face up into quarters . Okay
06:36	, so now you know how the second and minute
06:38	hands work . When the second hand goes all the
06:40	way around , the minute hand increases by one .
06:43	But what happens when the minute hand eventually goes all
06:46	the way around and has counted out 60 minutes ?
06:49	If you paid close attention at the beginning of the
06:51	video , you probably know the answer . 60 minutes
06:55	equals one hour . So when the minute hand goes
06:57	all the way around , it means one hour of
07:00	time has passed . That means we're going to need
07:02	to add the hour hand back to our clock to
07:04	keep track of ours . But the hour hand doesn't
07:07	use the 60 marks on the edge of the clock
07:09	in the same way that the other hands do .
07:11	Why not ? Because there aren't 60 hours in a
07:14	day . There's only 24 . If the hour hand
07:16	just moved one mark for each hour , it wouldn't
07:19	make it all the way around the clock face in
07:21	a single day . Ideally , it would be nice
07:23	if we could have the hour hand go around the
07:25	clock once per day . But unfortunately , the 60
07:29	marks on the clock don't divide evenly by 24 .
07:32	That means you can't find a nice hole . Number
07:35	two . Skip count to 24 by , for example
07:38	, if you had the hour hand move to marks
07:40	for each hour , it's still want to go far
07:42	enough to make it all the way around the clock
07:44	in a day . And if you had it moved
07:46	three marks for each hour , it would go too
07:48	far . Fortunately , the inventors of the clock came
07:51	up with a clever compromise . They realized that even
07:54	though 24 hours doesn't divide evenly into 60 half of
07:58	a day , which is 12 hours , does 60
08:02	divided by 12 equals five and five is a nice
08:05	hole . Number two skip count by in fact ,
08:07	we already have bigger marks on our clock face every
08:10	five marks , which makes this idea really convenient If
08:14	the hour and minute hands start pointing straight up as
08:17	the minute hand goes all the way around the clock
08:19	, counting out 60 minutes , the hour hand will
08:22	slowly move past the first five marks , which means
08:25	one hour has passed then , as the minute hand
08:28	goes all the way around again . The hour hand
08:31	will move past the next five marks , which means
08:33	that two hours will have passed . This continues on
08:36	until the hour hand makes it all the way around
08:38	the clock and gets to the 12 hour mark back
08:40	at the top , just like with minutes and seconds
08:43	. The top position on the clock represents both the
08:46	beginning and the end of the counting sequence for minutes
08:49	and seconds . That means the top position represents both
08:52	60 and zero before the hour hand . That top
08:55	spot represents both 12 and zero . Of course ,
08:59	12 hours is only half the day . That means
09:01	in order for this clock to keep track of one
09:03	whole day , the hour hand needs to make to
09:06	full trips around the clock face . It counts out
09:09	12 hours the first half and then 12 more for
09:12	the second half . That means that each hour mark
09:14	is passed twice during the day , so we need
09:16	a way to distinguish them . And that's where I
09:19	am and PM can help us out . AM stands
09:22	for Anti Meridian , which just means before Noon and
09:26	PM stands for post Meridian , which just means afternoon
09:30	to see how the AM and PM labels work with
09:32	the 12 hours on our clock face to keep track
09:35	of a full day . Let's compare them to a
09:37	simpler modern timekeeping system called the 24 hour clock Mhm
09:41	. In that system , the 24 hours of the
09:43	day are just labeled zero through 23 . In other
09:47	words , at the beginning of the day , which
09:49	happens to be midnight , the time is zero hours
09:52	and zero minutes . As the hours passed by ,
09:55	you eventually get to the time 23 hours and zero
09:58	minutes , which means you're starting the 24th hour of
10:00	the day . After that last hour passes , it
10:03	starts back over at zero for the next day on
10:06	the traditional clock face at midnight , the hour hand
10:09	is pointing straight up at 12 . So instead of
10:12	calling at zero o'clock , we call it 12 midnight
10:15	or 12 a.m. Then the 1st 12 hours of the
10:18	day pass one by one , using the A M
10:20	label , 1 a.m. Two a . M . 3
10:23	a.m. on up to 11 a.m. When the hour hand
10:27	gets to 11 a.m. you're beginning the 12th hour of
10:29	the day , and as soon as the 60 minutes
10:32	of that , our passed by the hour hand will
10:34	be back up at the top of the clock ,
10:36	pointing at 12 again . But this time we're going
10:38	to call that position 12 noon or 12 PM Then
10:42	the clock continues on counting out the last 12 hours
10:45	of the day using the PM label . One PM
10:48	two PM three PM on up to 11 p.m. When
10:52	the hour hand gets to 11 p.m. It means you're
10:54	starting the last or 24th hour of the day .
10:57	After that . Last hour passes the hour hand points
11:00	straight up at 12 again , which is now 12
11:02	midnight or 12 a.m. and the cycle starts all over
11:06	for the next day . Let's briefly summarize what we've
11:09	learned about the clock so far before moving on to
11:11	a few examples of telling time . Each time the
11:15	second hand rotates all the way around the clock ,
11:17	one minute has passed and the minute hand advances one
11:20	mark each time the minute hand goes all the way
11:23	around the clock , one hour has passed and the
11:25	hour hand advances five marks each time the hour hand
11:29	goes around the clock , 12 hours have passed ,
11:31	which is half a day . The 1st 12 hours
11:34	are called the A M hours , and the 2nd
11:36	12 hours are called the P M hours . If
11:39	this is your first time learning how Oclock works ,
11:41	it might seem kind of confusing . But don't worry
11:45	. The more you practice looking at a clock and
11:47	noticing which hands are pointing to , which marks the
11:49	faster you'll be able to tell what time it is
11:51	. In fact , let's practice that a few times
11:54	now so you can get the hang of it before
11:55	doing more practice on your own . Let's start with
11:58	this clock face . What time of day is it
12:00	displaying ? The hour hand is past the seven ,
12:03	but not to eight yet , so the hour is
12:05	seven . The minute hand is pointing directly at the
12:08	three , but remember , that's the third group of
12:11	five marks for counting minutes or seconds . So it's
12:13	pointing at the 15 minute mark , and the second
12:16	hand is pointing straight up , which is the zero
12:18	second mark . So the time is seven hours ,
12:21	15 minutes and zero seconds . Oh , and that's
12:25	how you write time . Using numbers . You write
12:27	the hours first , then minutes and then seconds if
12:29	necessary , all separated by colons . What is this
12:33	? 7:15 a.m. or P M . To tell that
12:36	you need to know if it's before noon or afternoon
12:39	. The halfway point of the day Books or tests
12:41	sometimes give you a clue about whether the time is
12:44	before noon or afternoon so you can figure it out
12:46	. Or they may just tell you if it's a
12:48	M or P . M , in this case ,
12:50	were given the clue . Soon the sun will set
12:53	, so we know it's afternoon or 7 15 PM
12:57	How about this example ? What time is this clock
13:00	displaying the hour hand is passed the 10 , but
13:03	not to 11 yet , so the hour is 10
13:06	. The minute hand is just past the fourth ,
13:08	which is the 20 minute mark , but it's not
13:10	too 21 yet , so the minute is 20 and
13:13	the second hand is pointing at the nine , which
13:15	is the 45 2nd mark . So the time is
13:18	10 hours , 20 minutes and 45 seconds , and
13:21	this time you're given the clue . It's a beautiful
13:24	morning . So you know that it's 10:20 a.m. Since
13:27	morning comes before noon . And finally , what time
13:30	of day is this clock display ? The hour hand
13:32	has passed the 12 , but not yet to the
13:34	one . So it's 12 something . The minute hand
13:37	is pointing just a hair past the six , which
13:40	is the 30 minute mark . So the minute is
13:42	30 and there's no second hand on this clock .
13:44	Not all clocks had them , so we're only concerned
13:47	about the time to the nearest minute . In this
13:49	example . Lastly , this clock faces actually labeled a
13:53	m . So we know that the time of day
13:55	is 12:30 a.m. which is 30 minutes past midnight .
13:59	All right , so now you know how seconds ,
14:01	minutes , hours and days all relate to each other
14:05	. You also know how a traditional clock works to
14:07	help you keep track of these units of time as
14:09	they pass . By and importantly , you've learned how
14:13	to read the hands of the clock face so that
14:15	you can tell what time of day it is .
14:16	Remember that the way to get good at anything in
14:19	math is to practice , So be sure to practice
14:21	telling time on your own as always . Thanks for
14:24	watching math antics , and I'll see you next time
14:27	. Learn more at math antics dot com .

Summarizer

DESCRIPTION:

Learn More at mathantics.com Visit http://www.mathantics.comâ for more Free math videos and additional subscription based content!

OVERVIEW:

Math Antics - Telling Time is a free educational video by Lumos Learning.

This page not only allows students and teachers view Math Antics - Telling Time videos but also find engaging Sample Questions, Apps, Pins, Worksheets, Books related to the following topics.