Being able to tell and work with time is a very valuable skill. In order to tell time, there are several key points to remember. We measure time in seconds, minutes, hours, days, weeks, months, and years. On a clock, we measure time in hours and minutes (and sometimes seconds). On a calendar, we measure time in days, weeks, months, and years. This section will go through telling time on a clock—using minutes and hours. In order to work with minutes and hours, you must remember that there are 60 seconds in a minute, and 60 minutes in an hour. There are 24 hours in one day.
A clock is a device used to tell time. Clocks measure time in hours and minutes, and have an hour hand (that moves forward one clock number every hour) and a minute hand (that moves forward one tick every minute—it moves forward one clock number every 5 minutes). A clock is split up into 12 sections, and each section is worth 5 minutes (because 5 x 12 = 60, and there are 60 minutes in an hour). One complete trip around the clock by the minute hand means that one hour has passed. When you read a clock, you look at the hour hand first, and then you look at the minute hand. The hour hand is shorter, and the minute hand is longer—this is how you tell them apart. A normal clock looks like this:
The blue numbers are standard on all clocks—these are clock numbers. You will not see the orange numbers on normal clocks the way they are on the outside of this clock, but these are the minute marks—thus, every 1 clock number is equal to 5 minutes. It can be even further broken down like this:
Now, you can see that the orange numbers on the outside count from 1 to 60. These numbers represent each minute of an hour.
Now, we’ll add in the hour and minute hands. Remember, the hour hand is shorter, and the minute hand is longer. We’re going to set our clock to say 1 o’clock.
Notice that our clock hands have arrows—some clocks have hands with arrows, and others do not. We will show ours with arrows.
Reading a clock takes practice, but after you learn how, it’s very easy to do! First, you’re going to locate the hour hand. The hour hand is the shorter of the two clock hands. It moves from one clock number to the next every hour, and it makes one complete rotation around the clock every 12 hours (since there are 12 clock numbers on each clock). Look at which clock number the hour hand is pointing to. That is the number you will use for the hour. Many times, the arrow will not be pointing exactly at the number; in that case, you would look at which number it was at most recently. For example, if the hour hand is half way between the 2 and the 3, you would use 2 as the hour number. The only way you can use a specific number for the hour number is if it has already passed the number in its rotation around the clock. So, even if the hour hand is very close to the 3, you would still say 2 unless the hand has reached, or passed, the 3. Here’s an example of what we mean:
Here, you can see that the hour hand is a little more than half way between the 1 and the 2. Even though it is closer to the 2, we would still say that 1 is our hour number because the hour hand has not passed 2 yet.
Now let’s talk about the minute hand. The minute hand is the longer of the two hands. It points to the minutes that have passed since a new hour began. It makes one rotation around the clock every hour. If the minute hand is pointing to a clock number, that means the number of minutes is a multiple of 5 (5, 10, 15, 20 etc) and you would give that number as the number of minutes. For example, if the minute hand is pointing to the clock number 1, you would say 5 minutes. If the minute hand is pointing to the clock number 6, you would say 30 minutes. You can easily figure this out by counting by 5s around the clock. However, if the minute hand is in between two clock numbers, you have to count by 5s until you get to the nearest clock number, and then count up by ones to figure out how many minutes you have. Take this as an example:
Notice that the hour hand is between the 7 and the 8. To count the minutes, you would count each clock number—remember to count by fives!—until you get to the 7 clock number. You should have counted 35 minutes. Then, you would estimate where the hand is actually pointing. Some clocks have little slashes for each minute, while others do not. In our clock example, we have the numbers written around the edge to make it easier to read.
So, in your mind, extend the minute hand all the way to the edge, and read how many more minutes it has passed. In our example, the minute hand is pointing to the 38. Normally, you would see that it’s at the 3rd mark after the clock number, so you would add 3 to 35 and get 38. Since ours is written out, we can just look and see where it’s pointing, and read it that way.
Thus, to tell the time, you would say it is 1:38, which is read “one thirty-eight.”
Once you can read the hour and minutes, you may also be asked whether it is AM or PM. This is not read from the clock, but rather from what time of day it is. AM runs from midnight (12:00) to 11:59 (one minute before noon). At noon, it becomes PM, and PM goes from noon (12:00) to 11:59 (one minute before midnight). Many people make generalizations and say that AM is when it’s light outside, and PM is when it’s dark outside. But don’t fall into this trap! That’s not entirely true. At 12:00 AM, it is dark outside, because it is the middle of the night. Around 5:00 or 6:00 AM (depending on the time of year) the sun comes up, and it is light out from about 6:00 AM until about 7:00 or 8:00 PM. Thus, at noon (12 PM), and until around 8:00 PM, it is still light outside! Around 7:00 or 8:00 PM, the sun goes down, and it gets dark out. It gets dark around 8:00 PM, and is dark until the next morning, when the sun comes up around 6:00 AM. As you can see, part of the AM is spent in the dark, and part is spent in the light; part of the PM is spent in the light, and part is spent in the dark! Sometimes, you’ll be asked to answer questions based on whether the time is AM or PM. For example, what are you doing at 12:00? If it were 12:00 AM, you’d probably be sleeping! However, if it were 12:00 PM, you’d probably be eating lunch!
Let’s practice this. Answer the following questions:
Now you’re getting the hang of it! So if someone asks you to tell whether it’s AM or PM when you’re telling time, you’ll be able to.
Elapsed time means how much time has passed from one point to another. Being able to measure elapsed time is important because you will be able to easily figure out starting and ending times of events, as well as how much time you will need, total, to get somewhere, get home, and so on.
Measuring elapsed time involves knowing the start time and end time of an event, and then figuring out how much time was in the middle. For example, you might be asked to calculate the elapsed time if you went to the park at 1:00 PM and came back home at 3:00 PM, how much time did you spend at the park?
In order to solve this problem, you would need to figure out how many hours and minutes are between 1:00 and 3:00 PM. The easiest way to do this is to “count up” from 1:00 to 3:00. In order to do this, you would think: from 1:00 PM to 2:00 PM is one hour. From 2:00 PM to 3:00 PM is one hour. Therefore, we add 1 hour + 1 hour = 2 hours total. Thus, 2 hours have elapsed.
You can also set up a subtraction problem in order to solve this, it would look like this:
As you can see, in order to subtract we put the ending time at the top of our problem, and subtracted our starting time. This is how you would set up any time subtraction problem.
Now, let’s try a harder problem. This time, you’re going to a birthday party. The party starts at 1:30 PM and lasts until 4:00 PM. How long does the party last?
You have two options in order to solve this problem. The first option is to count up from 1:30 to 4:00. To do this, you would count by hours first until you get close to 4:00, and then count how many minutes are left. You know that from 1:30 to 2:30 is one hour. From 2:30 to 3:30 is another hour. If you count from 3:30 to 4:30, you will have gone too far, so you would stop counting hours at 3:30. So far, you have 2 hours. Now, you need to count how many minutes you have left. Well, you know that there are 60 minutes in an hour. You’re starting at 30 and going to 60, which means you have 30 minutes to get to 4:00. Now, you add the hours and minutes together, and come up with 2 hours and 30 minutes.
The other option in solving this problem is to set up a subtraction problem. It would look like this:
Notice that we had to borrow in order to subtract the half hour (30). When we borrowed from the 4, we crossed out the 4 and made it a 3 (that’s normal) but then instead of putting a 1 in front of the next digit, we added 60 to the minutes of the top number. Now, we can do 60 – 30, and subtract the rest normally, like this:
Notice that our answer looks like this: 2:30, but when you report your answer, you would write 2 hr 30 min. The number before the colon is hours, and the number after the colon is minutes.
Now let’s try a few practice problems. We’ll give you the start and end time of an event, and you can figure out how much time elapsed during the event.
If you used method one, you would count forwards from 8:45 to 11:30. You would count 8:45 to 9:45 as one hour, then 9:45 to 10:45 as another hour. You would then stop and realize that if you counted an entire hour more, then you would be at 11:45, and would have passed 11:30. Therefore, you know that you need to stop and 10:45 and count forward using minutes for the rest. You know that from 10:45 to 11:00 is 15 minutes, and then from 11:00 to 11:30 is 30 minutes, so you would add those two numbers together, 15 + 30 = 45. Now, go back and remember the 2 hours you had already, so you end with a total of 2 hrs 45 min.
If you used method two, you would have written out a subtraction problem starting with 11:30 and subtracting 8:45. You would have to borrow, and add 60 to the top number, like this:
Notice that the 30 of the top number gets 60 added to it, resulting in 90. After that, it’s simply normal subtraction, ending with 2:45. Remember, the number before the colon is hours, the number after the colon is minutes, so your answer is 2 hrs 45 min.
If you used method one, you would count forwards from 1:55 to 9:20. You would count whole hours from 1:55 to 8:55, which gives you 7 hours. You realize that you cannot go past 8:55 because adding another hour would take you past the time Kim left work. Once you stop at 8:55, you need to count up by the minutes. From 8:55 to 9:00, there are 5 minutes. From 9:00 to 9:20, there are 20 minutes. When you add these all together, you would get 7 hrs 25 min.
The second method would involve setting up a subtraction problem. You would use 9:20 as the top number because that is the ending time. You would use 1:55 as the bottom number, that’s getting subtracted, because that’s the beginning time. You would need to borrow from the 9 and add 60 to the 20 minutes on top. Then your subtraction becomes 80 – 55. You need to borrow again in order to complete this, but this time you would borrow as normal and put a 1 in front of the next digit, like this:
Thus, your final answer is 7 hrs 25 min.