Time Intervals

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Time Intervals

What are time intervals? Imagine you are invited to your friend's birthday party. On the day of the party, you arrive at two thirty-five and leave at five o'five. Do you know how long you spent at your friend's place? To figure that out, we have to have a look at the time interval of your stay.

You might ask yourself, what does the term time interval mean? The definition for a time interval is how long an activity takes from beginning to end. The following text teaches you how to find and calculate a time interval.

Time Interval Calculation

We can use a clock to calculate the interval of time it takes to complete a task or activity. You can skip count forward from the start time to the end time to find the time interval, or you can skip count backward from the end time to the start time to find the time interval.

Step # What to do
1 Find the start time and the end time on the clock.
2 Skip count forward from the start time to the
end time to find the time interval.
You can skip count in fives or tens.

To calculate the minutes, we can skip count five minutes or ten minutes. When you calculate the interval of time, it can help you find which interval of time is the longest or shortest. Let’s take a look at a time interval example.

Time Interval Calculation – Example

On the day before the birthday, you are baking some desserts to bring along to the party and want to calculate the interval time it takes to bake each item. Remember, the time interval meaning is how long an activity takes from beginning to end.

You put the cake in the oven at four thirty-five and took it out at six o’five. The first step in a time interval calculation is to find the start time and the end time on the clock.

The second step is to skip count forward from the start time to the end time to find the time interval. Alternatively, you could skip count backward from the end time to the start time to find the time interval.

If we count forward from the start time to the end time, we can skip count by one hour first, which brings us to five thirty-five. From there we can skip count by tens until we reach six o’five. It takes three tens to reach six o'five, so we know the time interval it takes to bake the cake is one hour and thirty minutes.

If we skip count backward from the end time to the start time, we can also skip count by one hour first, which brings us to five o’five. From there we can skip count by tens until we reach four thirty-five. It takes three tens to reach four thirty-five, so the time interval it takes to bake the cake is one hour and thirty minutes.

As you can see, there are two different ways to do the time interval calculation, but we still get the same time interval.

Time Interval Calculation – Summary

Remember, a time interval determines how long an activity takes from start to finish. We can calculate the time interval using two easy steps:

• Step 1: Find the start time and the end time on the clock.
• Step 2: Skip count forward from the start time to the end time to find the time interval, or skip count backward from the end time to the start time. You can skip count in fives or tens.

So, how long was the time interval of your stay at the party from two thirty-five to five o'five? Let's count forward: We can skip count by two hours first, which brings us to four thirty-five. Then, we skip count three tens until we reach five o'five. The time interval of your celebration is therefore... two hours and thirty minutes! Well done. If you want to practice some more, take a look at the time interval worksheets and exercises.

TranscriptTime Intervals

Zuri is preparing treats for Freddie's surprise birthday party. She's baking buns, biscuits, and a cake. Zuri is clearly the G.O.A.T when it comes to baking. Let's see if we can calculate how long Zuri bakes each item for by finding the "Time Intervals" on an analogue clock. A "time interval is how long an activity takes from beginning to end." Time intervals can be calculated by counting on the clock in fives, tens, and the hour. You can count FORWARDS from the start time to the end time or you can count BACKWARDS from the end time to the start time. Let's see how long it took Zuri to bake the biscuits! Zuri put the biscuits in the oven at twenty past two and took them out of the oven at five past three. How long did they take to bake? The first step is to find the start time and the end time on the clock. They started baking at twenty past two and the end time is five past three. The second step is to count FORWARDS from the start time to calculate the time interval. Here we can count in fives. Remember: Each number on the clock represents 5 minutes. Five, ten, fifteen, twenty, twenty-five, thirty, thirty-five, forty, forty-five How long did the biscuits take to bake?

The time interval it took for Zuri to bake the biscuits is forty-five minutes. Now let's see how long it took for Zuri to bake the buns. Zuri put them in the oven at quarter past three right after the biscuits came out. She took them out at twenty five past four. How long did the buns take to bake? The first step is to find the start time and the end time on the clock. Can you find the start time and the end time on the clock?

They started here at quarter past three and ended here at twenty five past four. This time we will count BACKWARDS from the start time to calculate the time interval. Since we know from quarter past three to twenty five past four is more than an hour, we can count BACKWARDS by one hour first. That brings us to twenty five past three. Can you count BACKWARDS in fives until we reach quarter past three?

Five...ten! How long did it take for the buns to bake?

The time interval it took to bake the buns is one hour and ten minutes. Finally, Zuri put the cake in the oven at twenty five to five. She took the cake out at five past six. How long did it take to bake the cake? Remember, the first step is to find the start time and the end time on the clock. The second step is to count FORWARDS or BACKWARDS to calculate the time interval. This time you can choose to count FORWARDS or BACKWARDS. So, how long did it take to bake the cake?

If you decided to count FORWARDS from the start time you could have counted forwards one hour. That brings you to twenty five to six. From there, you could have counted in tens until you reached five past six. Ten, twenty, thirty The time interval it took to bake the cake is one hour and thirty minutes or an hour and a half. If you decided to count BACKWARDS from the end time, you could have counted backwards one hour. That brings you to five past five. From there, you could have counted in tens until you reached twenty five to five. Ten, twenty, thirty Counting backwards we also find the time interval is one hour and thirty minutes or an hour and a half. Remember, when you are trying to identify the time interval, you are trying to see how long an activity takes from beginning to end. The first step is to find out the start time and the end time. The second step is to count FORWARDS, or you can count BACKWARDS. We can identify time intervals by counting on the clock in fives, tens, and also by the hour. Oh! It looks like it's time to get ready to surprise Freddie...shhh! Quick, everybody hide!" "SURPRISE!"

Time Intervals exercise

Would you like to apply the knowledge you’ve learnt? You can review and practice it with the tasks for the video Time Intervals.
• Choose the set of clocks that match the time interval.

Hints

Count forwards in intervals from the start time or count backwards in intervals from the end time.

Remember to count in fives between each number.

Solution

Counting Forwards:

• Starting at 3:15 we can count forwards 1 hour.
• That means the hour hand moves from 3 to 4, which brings us to 4:15.
• After counting forwards to reach 4:25, we get 10 minutes.
• The time interval it took was 1 hour and 10 minutes.
Counting Backwards:
• Starting at 4:25 we can count backwards 1 hour.
• That means the hour hand moves from 4 to 3, which brings us to 3:25.
• After counting backwards to reach 3:15, we get 10 minutes.
• The time interval it took was 1 hour and 10 minutes.

• Match the time interval to the clocks.

Hints

Count forwards in intervals from the start time or count backwards in intervals from the end time.

Has more than an hour passed?

Remember to count in fives between each number.

Solution

Counting backwards:
For the first set of clocks:

• Starting at 1:35 we can count backwards to reach 12:50, which is 45 minutes.
• The time interval it took was 45 minutes.
_____________________________________________________________________________________ For the other clocks counting backwards:
For the second set of clocks:
• Starting at 8:30 we can count backwards 1 hour. That means the hour hand moves from 8 to 7, which brings us to 7:30.
• After counting backwards to reach 7:25, we get 5 minutes.
• The time interval it took was 1 hour and 5 minutes.
For the third set of clocks:
• Starting at 3:40 we can count backwards to reach 2:45, which is 55 minutes.
• The time interval it took was 55 minutes.
For the last set of clocks:
• Starting at 7:45 we can count backwards 1 hour. That means the hour hand moves from 7 to 6, which brings us to 6:45.
• After counting backwards to reach 6:15, we get 30 minutes.
• The time interval it took was 1 hour and 30 minutes.

• How long did each task take?

Hints

Count forwards in intervals from the start time or count backwards in intervals from the end time.

Remember to count in fives between each number.

Solution

Counting forwards:
For the first set of clocks:

• Starting at 10:15 we can count forwards to reach 11:05, which is 50 minutes.
• The time interval it took was 50 minutes.
_____________________________________________________________________________________ For the other clocks counting forwards:
For the second set of clocks:
• Starting at 6:25 we can count forwards 1 hour. That means the hour hand moves from 6 to 7, which brings us to 7:25.
• After counting forwards to reach 7:50, we get 25 minutes.
• The time interval it took was 1 hour and 25 minutes.
For the third set of clocks:
• Starting at 3:40 we can count forwards 1 hour. That means the hour hand moves from 3 to 4, which brings us to 4:40.
• After counting forwards to reach 4:55, we get 15 minutes.
• The time interval it took was 1 hour and 15 minutes.
For the last set of clocks:
• Starting at 12:05 we can count forwards to reach 12:50, which is 45 minutes.
• The time interval it took was 45 minutes.

• What's the time interval?

Hints

Try solving one of two ways:

• Count the time interval backwards by starting at the end time.
• Count forwards from the start time and work out which interval and end time matches.

Has more than an hour passed?

Remember to count in fives between each number.

Solution

Counting backwards:
Starting at 4:05 and the time interval 1 hour and 30 minutes:

• We can count backwards 1 hour. That means the hour hand moves from 4 to 3, which brings us to 3:05.
• After counting backwards 30 minutes, we stop at 2:35.
_____________________________________________________________________________________ For the other clocks counting backwards:
Starting at 3:05 and the time interval 45 minutes:
• We can count backwards 45 minutes, which brings us to 2:20.
Starting at 3:40 and the time interval 1 hour and 25 minutes:
• We can count backwards 1 hour. That means the hour hand moves from 3 to 2, which brings us to 2:40.
• After counting backwards 25 minutes, we stop at 2:15.
Starting at 3:20 and the time interval 35 minutes:
• We can count backwards 35 minutes, which brings us to 2:45.

• How long did it take Zuri to bake the buns?

Hints

Count forwards in intervals from the start time or count backwards in intervals from the end time.

Has more than an hour passed?

Remember to count in fives between each number.

Solution

Counting Forwards:

• Starting at 3:15 we can count forwards 1 hour.
• That means the hour hand moves from 3 to 4, which brings us to 4:15.
• After counting forwards to reach 4:25, we get 10 minutes.
• The time interval it took was 1 hour and 10 minutes.
Counting Backwards:
• Starting at 4:25 we can count backwards 1 hour.
• That means the hour hand moves from 4 to 3, which brings us to 3:25.
• After counting backwards to reach 3:15, we get 10 minutes.
• The time interval it took was 1 hour and 10 minutes.

• Which time intervals are wrong?

Hints

Count forwards from the start time or count backwards from the end time.

Has more than an hour passed?

Remember to count in fives between each number.

Two time intervals are wrong.

Solution

The second and last time intervals are correct.
The first time interval is 35 minutes, not 45 minutes.

• Starting at 6:25 we can count backwards to reach 5:50, which would be 35 minutes.
• The time interval it took was 35 minutes.
The third time interval is 1 hour & 40 minutes, not 2 hours & 30 minutes.
• Starting at 5:15 we can count backwards 1 hour. That means the hour hand moves from 5 to 4, which brings us to 4:15.
• After counting backwards to reach 3:35, we get 40 minutes.
• The time interval it took was 1 hour and 40 minutes.