Finding durations of time

A duration is a measurement of time. It tells you how long something lasts for.

You need to be able to calculate durations of time, so you can plan and organise the things you need to do.

You can measure a duration of time in seconds, minutes and hours.

• There are 60 seconds in 1 minute.

• There are 60 minutes in 1 hour.

Why not see how much you know about this topic already? Then complete the guide and see if you can beat your score.

You can calculate time durations using the hands on an analogue clock. Both a clock and a watch are very helpful for finding time durations, not just telling the time!

You can use them to count in lots of different intervals.

For example, you can count in 1 minute intervals and 5 minute intervals.

Let’s use a clock to solve this question.

Jamie starts eating a sandwich at 20 past 12 and finishes at 26 minutes past 12. ​How long does it take for Jamie to eat the sandwich?

Let’s compare the clocks.

Can you see that the hour hand is in the same place, but the minute hand has changed?

This means that it has taken Jamie a number of minutes to eat the sandwich.

Let's work out what that is.

If you add five minutes to the start time it will be 25 minutes past 12.

Then you need to one more minute to get to the finish time of 26 minutes past 12.

So it took Jamie 6 minutes to eat the sandwich.

You can check that using a timeline. A clock is like a circular timeline.

A timeline shows the same idea, but it is a straight line that you can count on.

Durations in hours

Let's look at another question.

Omi is having a birthday party. It starts at quarter past 4 and finishes 2 hours later.

What time does Omi's party finish?

Let's use a digital clock to add on 2 hours.

You can check this again with a timeline.

Durations in hours and minutes

Let's look at one more question

James is playing tennis. He plays for 1 hour and 25 minutes and finishes his game at 10 past 11.

What time does James start playing tennis?

For this question you need to count back because you are trying to find out the start time.

This means you need to imagine the hands of the clock moving anti-clockwise (backwards) around the clock face.

Let’s use a timeline for this question. We know James played for 1 hour and 25 minutes, so let’s count back the hour first.

Now count back the minutes. You need to count back 25 minutes.

You can do this in 5 jumps of 5 minutes along the number line.

James started playing tennis at 9:45am.

You can also say James started playing tennis at quarter to 10.

Example 2

Example 3