Lesson video

Hi Year Six, welcome to our final lesson in the decimals and measures topic.

Today, we'll be converting between units of time.

All you need is a pencil and a piece of paper.

So pause the video and grab your equipment if you haven't done so already.

Here's our agenda for today's lesson.

We'll be converting between units of time, starting with a quiz to test your knowledge from our previous lesson.

Then we'll look at converting time, equivalent times and solving problems with time.

You'll do some independent learning and then a final quiz.

So let's start with the initial knowledge quiz.

Pause the video now and complete the quiz and click Restart once you're finished.

So let's start with a Do Now.

You have a table here with time in 12 hour format, 24 hour format and in words.

Pause the video and complete the table.

So here are your solutions.

Check through them and have a look.

Have you put in whether it is in the afternoon, morning or evening, and have you put am and pm onto your timings as well? So let's jump straight in to working on converting time.

Now, when we convert metric units of measurement, which we've been doing in the last couple of weeks, we multiply or divide by 10, 100 or 1000 in order to convert.

So we know that one metre is equal to a hundred centimetres, so to convert from metres to centimetres, we multiply by a hundred.

100 centimetres is equal to 1,000 millimetres.

So to convert from centimetres to millimetres, we multiply it by 10.

And that we can apply it to units of metric measurement, which we've been doing this week.

But is this the same for when we convert units of time? Well, it's not because unlike metric units, time does not have what we call a base ten relationship.

You can't multiply or divide by a multiple of 10 in order to convert.

Therefore, converting between units of time requires bit more thought and some different strategies.

So let's begin with how you would describe one minute.

Pause the video now and write down anything that comes to mind when you think of one minute.

So here are some of the things that you may have thought of.

One minute is 60 times longer than one second.

One minute is 60 seconds.

One minute is one second multiplied by 60 or a 60th of an hour.

We could also say that it's one hour divided by 60 or it's 60 times shorter than one hour.

So then we look at the relationship here.

So 60 seconds is equal to one minute.

So that means that I can multiply one minute by 60 to find the number of seconds.

One multiplied by 60 is equal to 60.

And therefore, to convert from seconds to minutes, I can divide by 60.

So that's my conversion to go between minutes and seconds.

Let's have a look at minutes and hours.

So there are 60 minutes in one hour.

One hour is equal to 60 minutes.

So I can therefore multiply one hour by 60 to find the number of minutes.

And the other way I can divide minutes by 60 to find the number of hours.

So here are conversions between seconds and minutes and minutes and hours.

Let's move our thinking on.

So we know that to convert from seconds to minutes, we divide by 60 because there are 60 seconds in one minute, and then to convert from minutes to hours, we divide by 60 again.

To get from hours to minutes, we multiply by 60.

And minutes to seconds, we multiply by 60.

Now we just want to draw two things to your attention, where we often talk about time and we bring fractions into it as well.

So we may have heard of quarter of an hour, three quarters of an hour.

So just so it's on our radar, let's just think about how many minutes are there in quarter of an hour.

So remember an hour is 60 minutes, a quarter of 60 is 60 divided by four and that's 15.

So there are 15 minutes in quarter of an hour.

How many minutes are there in three quarters of an hour? Well if there's 15 in one quarter, then 15 multiplied by three gives us three quarters and that's 45 minutes.

So these are fractions of time that are really worth remembering.

We also have half an hour, which is half of 60 minutes, which is 30 minutes.

Now let's move our thinking on to other parts of time.

So let's think about what is the relationship between hour, day and week.

I'd like you to pause the video now and make any notes that you can think of about this relationship.

So here are some thoughts.

One hour is one 24th of a day, because one day is equivalent to 24 hours.

One day is one seventh of a week because one week is equivalent to seven days.

And finally, one week is equivalent to 168 hours because if we have 24 hours in a day and seven days in a week, 24 multiplied by seven gives us 168 hours.

So what we're just thinking about here is just getting our head around all the different elements of time.

Let's look even further.

Now we're thinking about these units of time, months, years, decades, centuries, millennium.

Can you pause the video now and write any notes around thinking about the theme of notes that we've been writing in the last few slides? Pause the video now.

So I started with a month, and I wrote that 12 months is equivalent to one year.

And there are between 28 and 31 days in a month.

So if you think about your months rhyme, we know that there are 30 days in September, April, June, and November.

All the rest have 31 except February, which has 28 days each year, but 29 in a leap year, which is once every four years.

So then I moved on to years.

So in a non leap year, there are 52 weeks and one day, which is 365 days.

And in a leap year, there are 52 weeks and two days, which is 366 days.

A decade is equivalent to 10 years.

A century, a hundred years and a millennium, a thousand years.

So now we're going to move on to look at equivalent times, and I'd like you to use what we've learned about converting between seconds, minutes, and hours and all of our other knowledge about days, weeks, months, and years to match the equivalent times into sets.

I can tell you that there are four sets and there is one odd time that doesn't match into any set.

So pause the video now and match the equivalent times into sets.

So we start with quarter of an hour.

That matches up with 15 minutes, which is equivalent to 900 seconds.

So 15 multiplied by 60 is equal to 900 seconds.

Then we'll go on to two and a half days.

That much is up to 60 hours.

So two lots of 24 plus 12, which is half a day, gives us 60 hours.

And then from hours to minutes, 60 multiplied by 60 gives us 3,600 minutes.

And moving onto December, December is 31 days and 31 days is 24 hours in one day.

So in 31 days, 31 multiplied by 24 hours gives us 744 hours.

And then our final set was three weeks, which is equivalent to 507 hours.

So to calculate that, we think about how many days are in three weeks, three times seven is 21 days and there's 24 hours in one day.

So in 21 days, it's 24 multiplied by 21, which gives us 504 hours.

And then your one day was the one that was the odd one out.

Now let's move on to solving problems involving the conversion of time.

So here's my first question.

What is 400 minutes in hours and minutes? So I need to think about what I already know about hours and minutes.

So one hour is equivalent to 60 minutes.

So I need to think about how many groups of 60 can be made from 400 minutes? And I can represent this using a bar model.

So I've got 400 minutes and I know using my knowledge of multiplication, that there are six groups of 60 in 400.

So six groups of 60 is 360 minutes.

And I know that if I had a seventh group of 60, that would take me to 420 minutes.

So that will be too many.

So six groups of 60, that's six hours and there's 40 left over.

So that's six hours and 40 minutes is equivalent to 400 minutes.

Let's look at another problem together.

So the average person sleeps for one third of their life.

So on average, how many years has a six year old child slept for? So we need to think of one third of six.

One third of six is two years.

So the average six year old has slept for two years of their life.

Now I want you to think about these two questions.

How many weeks is this? And how many days is this? So how many weeks is two years equal to? And how many days is two years equal to? Pause the video now while you calculate.

So how many weeks is this? There are 52 weeks in a year.

So two times 52 is equal to 104 weeks.

And how many days is this? Two years.

So one year is 365 days.

So two years is two multiplied by 365, which is 730 days.

Now it's time for you to do some independent learning.

So pause the video and complete your task and then click Restart once you're finished.

So for question one, a nice straightforward start, you were asked to match the equivalent times.

So one week is equivalent to seven days.

One day is 24 hours.

January is 31 days.

2016 was a leap year, so there were 366 days.

A decade is equal to 10 years.

And 1.

5 hours or one and a half hours is 90 minutes.

Then you were asked to order the times from shortest to longest.

And what I've done is I've just added some conversions on to help me with my thinking.

So I know that five weeks is 35 days, which is 840 hours.

I know two days is two lots of 24 hours, which is 48 hours.

I know that a thousand minutes, there are 16 lots of 60 with 40 leftover.

So 16 hours and 40 minutes.

And I know the month of March is 31 days and 31 times 24 is 744 hours.

So having everything in the same unit in hours really helped me to order them from shortest to longest.

So the shortest time is a thousand minutes.

Then two days, then 70 hours, then March, and then finally, five weeks.

In question three, we're looking at planets.

So the closer planet is to the sun, the less time it takes for the planet to complete one full orbit.

So the earth orbits the sun in approximately 365 days.

And we want to know how many hours is this.

So if one day is 24 hours, then 365 days is 365 times 24, which is equal to 8,760 hours.

Part b, the moon orbits the earth in 28 days.

And we need to know how many minutes this is.

So this is a two step problem.

First, we need to go to hours then minutes.

So 28 days, one day is 24 hours.

So 28 days is 24 times 28, which gives us 672 hours.

And then we convert to minutes.

We know that there are 60 minutes in one hour.

So in 672 hours, it's 672 multiplied by 60, which gives us 40,320 minutes.

And part c, Mars, which you can see here, takes 687 days to orbit the sun.

And we need to know how many weeks is there.

So we need to know how many lots of seven days are there in 687 days.

And they were 98 weeks, and 98 lots of seven days, and one day leftover.

For question four, we had to read the clock to help us with this question.

So Novie looks at the clock and she calculates that she has 1,200 seconds until the end of the school day.

So what time does school finish? So first of all, we can see that the time shown on the clock is, we assume it's the afternoon.

So it's 15:05 or 3:05 p.

m.

We need to convert seconds into minutes.

So we do that by dividing 1,200 by 60, which gives us 20 minutes.

So we need to find 20 minutes further on the clock, which is 3:25.

So 3:05 plus 20 minutes is 3:25 or 15:25.

Now it's time for your final quiz.

So pause the video and complete the quiz.

And then click Restart once you're finished.

Well done Year Six, that's the end of our decimals and measures unit.

In our next lesson, we'll be working on understanding percentages.

I'll see you then.