Example 1 : Find the elapsed time from 7:45 AM to 8:12 AM
First way:
Use an analog clock to count the minutes, an old analog clock with no batteries can be used, and a pencil to mark the start and end times. Here are some steps that would guide you:
Step 1: Draw the starting time.
Step 2: Mark the ending time.
Step 3: Count the minutes by 5s and 1s until you reach the ending time.
In this clock, the minute hand starts from 9 and stops at two places after 2. As we counted 5s, five times till 2, then the elapsed time till 2 is, 5 + 5 + 5 + 5 = 20 minutes.
Now the minute hand is two places beyond 2 so count 1 twice, and add it to the previous time:
1 + 1 = 2 and 25 + 2 = 27
So, the elapsed time from 7:45 AM to 8:12 AM is 27 minutes.
Another way of finding the elapsed time is by using a number line. Here are some steps which would help us understand this:
Step 1: Plot the starting time on a number line.
Step 2: Count forward until you reach the end time.
Step 3: Add the jumps to find the elapsed time.
So, from 7:45 to 8:00 we have 15 minutes,
from 8.00 to 8.12 we have 12 minutes
If we add up all the jumps then we get :
15 + 12 = 27 minutes
So, the elapsed time from 7:45 AM to 8:12 AM is 27 minutes.
Example 2:
Smith has 30 minutes to play outside before dinner. He has already played for 18 minutes. How much time does Smith have left to play?
Solution:
Smith is allowed only 30 minutes to play outside before dinner. He has already played for 18 minutes.
Time for which Smith already played (18 minutes) should be subtracted from 30 to find the time remaining for him to play
.
So, the time left for playing = 30 – 18
= 12 minutes.
Smith can play for 12 minutes more.
Example 3:
What is the time shown in the clock?
Solution:
Step 1: Look at the hour hand first.
The hour hand is between the 5 and 6.
So, it is after 5 o’clock and before 6 o’clock.
Step 2: Look at the minute hand.
Count by 5s from 12 to 2. We counted 5s twice from 12 to 2 as:
5 + 5 = 10,
Now the minute hand is also four places ahead of 2. So we will count four 1s :
1 + 1 + 1 + 1 = 4
So, the total number of minutes are, 10 + 4 = 14
So, the time is 5 :14
Example 3:
What is the time shown in the clock?
Solution:
Step 1: Look at the hour hand first.
The hour hand is between the 12 and the 1.
So, it is after 12 o’clock and before 1 o’clock.
Step 2: Look at the minute hand.
So, the time is 12:43.
Count by 5s from 12 to 1. We counted 5s eight times from 12 to 8:
5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 40
Now the minute hand is also three places ahead of 8. So we will count three 1s:
1 + 1 + 1 = 3
So, the total number of minutes are 40 + 3 = 43
So, the time is 12 :43 .
Example 4:
Cam boarded up a train at 3:55 PM and reached another station at 4:41 PM. Find the time elapsed by Cam from 3:55 PM to 4:41 PM.
Solution:
First method:
Use an analog clock to count the minutes. As mentioned earlier, an old analog clock with no batteries can be used, and a pencil to mark the start and end times. Here are some steps that would guide you:
Step 1: Draw the starting time.
Step 2: Mark the ending time.
Step 3: Count the minutes by 5s and 1s until you reach the ending time.
In this clock, the minute hand starts from 11(55 minutes) and stops at one place after 8(40 minutes). As we counted 5s, nine times till 8, then the elapsed time till 8 is, 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 45 minutes.
Now the minute hand is one place after 8, which shows 1 minute. Now let’s add it to the previous time:
45 + 1 = 46
So, the elapsed time from 3:55 AM to 4:41 AM is 46 minutes.
Another way of finding the elapsed time is by using a number line. Here are some steps which would help us understand this:
Step 1: Plot the starting time on a number line.
Step 2: Count forward until you reach the end time.
Step 3: Add the jumps to find the elapsed time.
So, from 3:55 to 4:00 we have 5 minutes,
from 4:00 to 4:41 we have 41 minutes.
If we add up all the jumps then we get :
45 + 1 = 46 minutes
So, the elapsed time from 3:55 PM to 4:41 PM is 46 minutes.
