Main content

### Course: 4th grade > Unit 14

Lesson 8: Converting units of time# Converting units of time

Learn to convert hours, minutes, and seconds. Created by Sal Khan.

## Want to join the conversation?

- how many second are there in a year(31 votes)
- 31,536,000 seconds(16 votes)

- what if it was 5 seconds ? How do you convert that into minutes?(8 votes)
- I think that would be 1/12 of a minute as 5 seconds is 5/60 of a minute. 5/60 simplified is 1/12.(9 votes)

- how many seconds are there in a century?(2 votes)
- There are 31,536,000 seconds in a century. This is because there are 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day, and 365.2425 days in a year on average (leap years are taken into account), and 100 years in a century. Thus, there are 60 * 60 * 24 * 365.2425 * 100 = 31,536,000,000 seconds in a century. (Mistake caught by shayanrahman0130486)(8 votes)

- it still doesn't make sense.. could you be more specific?(0 votes)
- So the video is trying to show you how to figure out how many seconds are in a given number of minutes or how many minutes are in a given number of hours. Instead of actually counting this out, you can just remember that one minute has sixty seconds in it and that one hour has sixty minutes in it, so if you have 7 minutes and you're trying to figure out how many seconds are in that. All you really need to do is multiply 7 by 60. Similarly, to find how many minutes are in a given number of hours, you do the same thing. If you're trying to find the number of seconds in a certain amount of hours, you would multiply by 3600. (the number of seconds in an hour)(12 votes)

- Thanks but what about 20 hours how many seconds would that be?(2 votes)
- That would be 72,000 seconds. Since there are 60 seconds in one minute and 60 minutes in one hour, there would be 3,600 seconds in one hour (60 x 60). You multiply that by 20 to get 72,000.(2 votes)

- how many hours are in a year?(1 vote)
- 8766 hours in 1 year. I depends on the months. Like Feburary has either a 28 or 29.(4 votes)

- how many mins are in 1,000 seconds(2 votes)
- There are about 16.67 minutes in 1,000 seconds(2 votes)

- At0:09, Sal says that 1 minute = 60 seconds by definition. Similarly, at1:40, Sal says, "We know by definition 1 hour = 60 minutes."

How were a second, minute, and hour defined? Why is 1 minute 60 seconds and 1 hour 60 minutes? What rationales do these facts rest on?(2 votes)- At0:09, Sal says that 1 minute = 60 seconds by definition. Similarly, at1:40, Sal says, "We know by definition 1 hour = 60 minutes."

How were a second, minute, and hour defined? Why is 1 minute 60 seconds and 1 hour 60 minutes? What rationales do these facts rest on?(1 vote)

- How many seconds are in a decade(1 vote)
- Decade represents value of 10 years.

We know that one year has + - 365 days (to make the calculations simple. So 10 * 365 days.

One day has 24 hours. Which means we got (days: 10 * 365) * 24 hours!

one hour has 60 minutes. so we got (days: 10 * 365) * (hours: 24) * (minutes: 60)

And one minute has 60 seconds.

So the whole looks like this:

(days: 10 * 365) * (hours: 24) * (minutes: 60) * (seconds: 60)

which is

10 * 365 * 24 * 60 * 60

which is

3650 * 24 * 3600

which is

315,360,000.

So there are 315,360,000 (315 millions, 360 thousand) seconds in a decate.(2 votes)

- I'm so confused! I've watched this video 2 times. HOW. DO. YOU. DO. THIS?(1 vote)
- It sounds frustrating! Try pausing the video at each step to understand it better, and take notes if that helps. If you're still stuck, maybe take a break and come back to it later with a fresh mind.(2 votes)

## Video transcript

We have multiple
lengths of time here, and they're measured in minutes. So what we want to
do is say, well, what's an equivalent
number of seconds? And so the first one is
pretty straightforward. 1 minute is equal to 60 seconds. By definition, a second
is 1/60 of a minute. But what about 5 minutes? Well, we could try
to visualize that. If 1 minute-- so let's say
that is 1 minute-- if that is equal to 60 seconds,
then 5 minutes-- let's just make
five copies of this. So that's 1, 2, minutes,
3, minutes, 4 minutes, and then 5 minutes. So you see that 5 minutes
would be 5 times 60 seconds. And 5 times 60 is 300. So here you have
so this is going to be 5 times 60, which
is equal to 300 seconds. So what about 10 minutes? Well, same idea. 10 times 60 is 600 seconds. And what about 60 minutes? Well, 60 minutes or 60 seconds
per minute times 60 minutes is equal to 3,600 seconds. So that's interesting. Let's take things a
little bit further other. Let's convert between
hours, minutes, and seconds. So let's start
off with something that's a little bit
more straightforward. Let's say that we have 1 hour. Well, we know by definition 1
hour is equal to 60 minutes. And how many seconds
is 60 minutes equal to? Well, we just figured that out. 60 minutes times 60
seconds per minute gets us to 3,600 seconds. Now, what about 2 hours? Well, it would be
the same exact idea. 60 minutes per hour,
if I have 2 hours, it's going to be 2 times 60. 2 hours times 60 minutes
per hour gets us to 120. Well, how many seconds
is that going to be? Well, there's a couple of
ways you could think about it. You could take 120 minutes
times 60 seconds per minute. Or you could say 2 hours
times 3,600 seconds per hour. So let's do it that way. So two 2 times 3,600 seconds per
hour gets us to 7,200 seconds. Now, what if we were
to say 10 hours? Well, once again, 10
times 60, 10 hours times 60 minutes per hour
would get us to 600 minutes. And if we want to think
in terms of seconds, 10 hours times 3,600 seconds
per hour gets us to-- well, it's going to be
3,600 tens, which would be 36,000, or 10 times
36 hundred, or 10 times 3,600.