91�ȱ�

Some words we can use to talk about time are seconds, minutes and hours.

• There are 60 seconds in 1 minute.

• There are 60 minutes in 1 hour.

Duration is how long something lasts.

When the minute hand on a clock moves from one number to the next, it has moved 5 minutes.

There are 12 numbers around a clock face, and each interval between the numbers is 5 minutes, so there are 12 × 5 = 60 minutes in an hour.

Look at the two clocks to the right.

Can you say how much time has passed between the first and second one?

Count the intervals between the numbers in 5 minutes.

The clock on the left shows the time as five past seven. The clock on the right shows twenty-five past seven.

We can count 4 intervals of 5 minutes between the two times, so 4 x 5 = 20.

The duration of time that has passed is 20 minutes.

There are other ways we can break time down more quickly and efficiently, in order to work out durations.

In a quarter of an hour there are 15 minutes.

In half an hour there are 30 minutes.

In three quarters of an hour there are 45 minutes.

It's useful to be able to work out time durations with digital clocks too. When we have bigger time durations to calculate, we can think in full hours, half hours, quarters or three quarters of an hour.

Can you work out the duration of time that has passed between these two digital clocks?

The digital clock on the left shows 06:45 or quarter to seven AM. The clock on the right shows 08:15 or quarter past eight AM.

There are different ways we could work this out, but a quick and efficient method is to add one hour to 06:45, to make 07:45, and then to add an extra half an hour, to bring the time to 08:15.

One hour = 60 minutes

Half an hour = 30 minutes

60 + 30 = 90 minutes

The duration of time that has passed is 90 minutes or one and a half hours.

When working out problems like this, we can think forwards or backwards in full hours, half hours, quarters or three quarters of an hour first, to get close to the answer, and then add or subtract intervals of 5 or fewer minutes to find the final answer.

Time durations problems

Can you work out the time durations in these sentences? Use a clock with hands to help you, if possible.

1. Amir decided to bake a cake. The cake went in the oven at 11 o'clock AM and came out again at quarter to twelve AM.

The cake took ____ minutes to bake.

2. Naomi went for a bike ride. She set off at 2:30 PM and came back at 3:45 PM.

Her bike ride lasted ____ minutes.

3. Asha practised playing her guitar, starting at 9:20 AM and finishing at 10:45 AM.

She practised for ____ minutes.

4. Charlie started playing computer games at 3:00 PM. He played for 45 minutes before having a half hour break. He then played for another 25 minutes. What time did Charlie finish playing?

Finished? Check your answers in this .

Using digital clock times to work out durations

Can you work out the durations of time that these trains spent at a station, between arriving and then departing again?

The first one has been done for you.

All done? Check your answers in this .