In our daily life, all the works are done at proper time and in proper time also. We walk daily with time and how our 24 hours are completed we can’t thought. We learn reading time from clock from our childhood. But, mostly we use 12 hour clock timing. We know that, in clock shortest hand is the hour hand and the longest hand is the minute hand as shown in figure.

And also we know that, between two numbers in clock there is a difference of 5 minutes. So when minute hand completes one rotation it means 1 hour.

And when hour hand completes one rotation it means 12 hours as shown in figure.

Thus,

1 hour = 60 minutes

1 minute = 60 seconds

- In both 12 hour and 24 hour clock, when hour hand completes one rotation means 12 hours.
- If minute hand completes one rotation then it means 60 minutes i.e. 1 hour.
- If second hand completes one rotation then it means 60 seconds or 1 minute.

- In above fig, there is a 12 hour clock, in which hour hand is on 5 and minute hand is on 3. Hence, the time is 5:15, but it may be a.m. or p.m.
- If it is 5:15 a.m. that means morning time and it represents 5 hours 15 minutes.
- If it is 5:15 p.m. that means evening time and it also represent 5 hours 15 minutes.

- The above figure shows the 12 hour clock time notation, in which hour hand is on 3 and minute hand is on 8. But here not mentioned clearly that a.m. or p.m.
- If it is 3:40 a.m. that means morning timing and it represents 3 hours 40 minutes.
- If it is 3:40 p.m. that means noon timing and it also represents 3 hours 40 minutes.

The following figure 1 shows the 12 hours clock and the second clock shows the 24 hours clock.

**Fig. 1) 12 Hour Clock**

**Fig. 2) 24 Hour Clock**

The difference between them is, in 12 hours clock time is expressed by considering 12 hours only. While in 24 hours clock time is expressed by considering 24 hours as shown in figure.

**Elapsed time:**

The elapsed time is the difference of time between the two events.

**For example:**

- We sleep daily suppose at 9:00 p.m. and wake up in morning at 6:30 a.m.
- Then the time of difference between these two times is the elapsed time. Here elapsed time is nothing but the how much time we sleep daily.
- Thus, directly by mental math we can say here, we daily sleep 9 hours 30 minutes.
- But, when the time is given in 24 hour clock we can’t calculate the elapsed time easily. We have to calculate on paper properly. To understand in detail we shall see following examples.

**Examples:**

**1) Meena slept at 9:34 p.m. and she wake up in morning at 5:45 a.m. then what is the elapsed time here.**

Elapsed time is nothing but the time difference between two events.

Thus, 9: 34 means 9 hours 34 minutes i.e. we can also write here 8 hours 94 minutes.

Since, 1 hour = 60 minutes

And 5:45 means 5 hours 45 minutes.

Hence,

Thus, here elapsed time is 3 hours 49 minutes.

**2) Rahul wants to go garden. He went garden at 6:15 p.m. and return to home at 7: 24 p.m. find the elapsed time here.**

Here elapsed time is nothing but the time spent by Rahul in garden.

6:15 means 6 hours 15 minutes i.e. we can also say it as 5 hours 75 minutes. Since 1 hour means 60 minutes.

And 7:24 means 7 hours 24 minutes.

Thus, the elapsed time is calculated as,

Thus, here elapsed time is nothing but the time spent by the Rahul in garden which is 1 hour 9 minute.

**3) The train from Agra depart at 14:30 and reach to Delhi at 17: 25. What is the elapsed time here?**

We know that, the clock used at railway station is the 24 hour clock. And also we know that, how to convert 24 hour clock time into 12 hour clock time.

Here, 14:30 is given, which is above 12 hours hence we subtract 12 from it and write it as p.m.

14:30 – 12:00 = 2:30 p.m. is the time in our 12 hour clock

And also, 17:25 is the 24 hour clock time which is above 12 hours, hence we subtract 12 hours from it and write it as p.m.

Thus, 17:25 – 12:00 = 5:25 p.m.

Now, the departure time is 2:30 p.m.

And arrival time is 5:25 p.m.

Here, the elapsed time is nothing but the time required by the train to reach Delhi from Agra,

Thus,

5:25 means 5 hours 25 minutes i.e. we can also say that 4 hours 85 minutes.

Hence,

Thus, the elapsed time here is the 2 hours 55 minutes.

In this way, we can find the elapsed time between any two events in 24 hour clock and 12 hour clock also