# Conversion Of Time

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

## 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}
1. \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}

120 s

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

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

900 s

Question 2:

Express the following time in seconds.

5 min = __________ s

Solution:

5 min = 5 × 60 s

= 300 s

300 s

Question 3:

Express the following time in seconds.

45 min = __________ s

Solution:

45 min = 45 × 60 s

= 45 × 6 × 10

= 2700 s

2700 s

Question 4:

Express the following time in seconds.

$1\frac {1}{2}$ h = __________ s

Solution:

1 h = 3600 s

$\frac {1}{2}$= 30 min

= 30 × 60

= 1800 s

$1\frac {1}{2}$= 3600 s + 1800 s

= 5400 s

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

3 min

1. 3000 s = 3000 ÷ 60

= 50 min

50 min

1. 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

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

2 min

Question 7:

Express the following time in minutes or hours and minutes.

300 s = ___________ min

Solution:

300 s

= 300 ÷ 60

= 5 min

5 min

## 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:

12-h clock

24-h clock

5:30 am

05:30

5:30 pm

17:30

10:30 am

10:30

10:30 pm

22:30

12:00 pm

12:00

12:00 am

00:00

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

08 50

b) 12:20 am = 00 20

00 20

c) 9:10 pm = 21 10

21 10

Question 2:

Express the following time in 24-hour clock.

2:35 am = __________

Solution:

2:35 am = 02 35

02 35

Question 3:

Express the following time in 24-hour clock.

11:15 pm = __________

Solution:

11:15 pm = 23 15

23 15

Question 4:

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

Solution:

19 15 is 7:15 pm in the evening.

(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

12:10 am

Question 7:

Express the following time in 12-hour clock.

20 15 = __________

Solution:

20 15 = 8:15 pm

8:15 pm

Continue Learning
Multiplication Whole Numbers
Multiplication And Division Decimals
Model Drawing Strategy Division
Fractions Factors And Multiples
Area And Perimeter 1 Line Graphs
Time

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