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Time Intervals

In this topic, we calculate the amount of time between two given times.

The clock below will help you. Count the number of hours clockwise (in the direction of the arrow) from the start time to the end time.

Example 1: A.M.

Calculate the difference in hours between the two times.
How many hours between 6:13am and 10:13am?   Hours:

Since the minutes are the same (:13), we only look at the difference between the hours.

Solution: Counting
Using the clock above, we start at 6:00am and count clockwise to 10:00am.
 6:00 am   →   7:00 am   →   8:00 am   →   9:00 am   →  10:00 am Count: 1 hour 2 hours 3 hours 4 hours

Counting from 6:00am to 10:00am is 4 hours.

Alternate Solution: Subtraction
10:00am - 6:00am = 10 - 6 = 4 hours

The answer is Hours:

Example 2: A.M. and P.M.

Calculate the difference in hours between the two times.
How many hours between 9:00am and 2:00pm?   Hours:

Solution: Counting
Using the clock above, we start at 9:00am and count clockwise to 2:00pm.
 9:00 am   →  10:00 am   →  11:00 am   →  12:00 pm   →   1:00 pm   →   2:00 pm Count: 1 hour 2 hours 3 hours 4 hours 5 hours

Counting from 9:00am to 2:00pm is 5 hours.

Alternate Solution: Subtraction
From midnight (12:00 am), 9:00 am is 9 hours away.
From midnight (12:00 am), 2:00pm is 14 hours (12 hours + 2 hours) away.
14 hours - 9 hours = 5 hours

The answer is Hours:

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