Conversion Of Time

In this article, we will be learning about the conversion of time and the 24-hour clock. The lesson objectives are: 

1. Conversion of time
2. 24-hour clock format

Topic Recap:

Conversion of Time

We can express time in hours and minutes to minutes. 

Example 1: 

1. \(1 \text{ h } = 60 \text{ min}\)
2. \(\begin{align}\\ 2 \text{ h }  &= 2 \times 60 \text{ min}\\        &= 120 \text{ min} \end{align}\)

3. \(\begin{align}\\ 3 \text{ h } 20 \text{ min } &= 180 \text{ min }+ 20 \text{ min }\\ &= 200 \text{ min } \end{align}\)

We can also express time in minutes to hours and minutes.

Example 2: 

1. \(180 \text{ min } = 3 \text{ h } 0 \text{ min }\)
2. \(\begin{align}\\ 400 \text{ min } &= 360 \text{ min }+ 40 \text{ min }\\                          &= 6 \text{ h } 40 \text{ min } \end{align}\)

1. Conversion Of Time

\(1 \text{ minute } = 60 \text{ seconds}\)

To express time from minutes to seconds, we multiply the number of minutes by 60. 

To express time from seconds to minutes, we divide the number of seconds by 60. 

\(1 \text{ hour} = 60 \text{ minutes}\)

To express from hours to minutes, we multiply the number of hours by 60. 

To express from minutes to hours, we divide the number of minutes by 60. 

Question 1: 

Express the following time in seconds.

1. \(\displaystyle{2} \text{ min} =\) __________ s
2. \(\displaystyle{2} \text{ h} =\) __________ s
3. \(\displaystyle{\frac {1}{4}} \text{ h} =\) __________ s

Solution: 

A. \(\begin{align}\\ 2 \text{ min } &= 2 \times 60\\ &= 120 \text{ s} \end{align}\)

Answer:

120 s

B. \(\begin{align}\\[2ex] 2 \text{ h } &= 2 \times 60\\       &= 120 \times 60\\        &= 7200 \text{ s} \end{align}\)

Answer:

7200 s

C. \(\displaystyle{\frac {1}{4} \text{ h}}\)

\(\because\)   \(1 \text{ h}\) = 60 min

\(\therefore\)   \(\displaystyle{\frac {1}{4} \text{ h}}\) = 60 min ÷ 4 = 15 min

\(\therefore\)   15 min = 15 × 60 s = 900 s

Answer:

900 s

Question 2: 

Express the following time in seconds.

5 min = __________ s

Solution:

5 min = 5 × 60 s

          = 300 s

Answer:

300 s

Question 3: 

Express the following time in seconds.

45 min = __________ s

Solution:

45 min = 45 × 60 s

            = 45 × 6 × 10

            = 2700 s

Answer:

2700 s

Question 4: 

Express the following time in seconds.

\(1\frac {1}{2}\) h = __________ s

Solution:

1 h = 3600 s

\(\frac {1}{2}\)h = 30 min

     = 30 × 60

     = 1800 s

\(1\frac {1}{2}\) h = 3600 s + 1800 s

         = 5400 s 

Answer:

5400 s

Question 5: 

Express the following time in minutes or hours and minutes. 

1. 180 s = __________ min
2. 3000 s = __________ min
3. 4500 s = __________ h __________ min 

Solution: 

1. 180 s = 180 ÷ 60 

             = 3 min

Answer:

3 min

2. 3000 s = 3000 ÷ 60 

               = 50 min

Answer:

50 min

3. 4500 s = 4500 ÷ 60 

               = 75 min

               = 1 h 15 min

OR

                    1 h = 3600s

4500 s - 3600 s = 900 s

                          = 900 ÷ 60 

                          = 15 min

Hence, 4500 s = 1 h 15 min       

Answer:

1 h 15 min

Question 6: 

Express the following time in minutes or hours and minutes. 

120 s = __________ min

Solution: 

120 s 

= 120 ÷ 60 

= 2 min

Answer:

2 min

Question 7: 

Express the following time in minutes or hours and minutes. 

300 s = ___________ min

Solution: 

300 s 

= 300 ÷ 60 

= 5 min

Answer:

5 min

Watch Our Video Lesson!

2. 24-Hour Clock Format

In the 24-hour clock, there is no need to add suffixes like am or pm. It is written in 4 digits, where the first two digits represent the hour and the last two digits represent the minutes. 

Time from midnight to noon: 

12-h clock = 12:00 am to 11:59 am

24-h clock = 00 00 to 11 59

Time from noon to midnight:

12-h clock = 12:00 pm to 11:59 pm

24-h clock = 12 00 to 23 59

Example:

Question 1: 

Express the following time in 24-hour clock.

1. 8:50 am = __________
2. 12:20 am = __________
3. 9:10 pm = __________

Solution: 

a) 8:50 am = 08 50

Answer:

08 50

b) 12:20 am = 00 20

Answer:

00 20

c) 9:10 pm = 21 10 

Answer:

21 10

Question 2: 

Express the following time in 24-hour clock.

2:35 am = __________

Solution: 

2:35 am = 02 35

Answer: 

02 35

Question 3: 

Express the following time in 24-hour clock.

11:15 pm = __________

Solution: 

11:15 pm = 23 15 

Answer:

23 15

Question 4: 

Which of the following clocks shows the time 19:15?

Solution: 

19 15 is 7:15 pm in the evening. 

Answer:

(4)

Question 5: 

Express the following time in 12-hour clock.

1. 03 30 = __________
2. 12 50 = __________
3. 17 45 = __________

Solution: 

1.  03 30 = 3:30 am
2. 12 50 = 12:50 pm
3. 17 45 = 5:45 pm

Question 6: 

Express the following time in 12-hour clock.

00 10 = __________

Solution: 

00 10 = 12:10 am

Answer:

12:10 am

Question 7: 

Express the following time in 12-hour clock.

20 15 = __________

Solution: 

20 15 = 8:15 pm 

Answer:

8:15 pm