Exercise 12.4

A. Write 12 hour clock time for the following.

1. 0530 hours = 5:30 a.m.

2. 1015 hours = _____________

3. 2350 hours = _____________

4. 0610 hours = _____________

5. 2020 hours = _____________

6. 1325 hours = _____________

B. Write 24 hour clock time for the following.

1. 3:15 p.m. = 1515 hours

2. 8:55 a.m. = _____________

3. 9:45 p.m. = _____________

4. 6:30 a.m. = _____________

5. 8:53 p.m. = _____________

6. 12:50 a.m. = _____________

C. Match the following.

1. 4:34 p.m. 1715 hours
2. 5:15 p.m. 2200 hours
3. 2:56 a.m. 0950 hours
4. 8 a.m. 1634 hours
5. 10 p.m. 0256 hours
6. 9:50 a.m. 0800 hours

Conversion of time

The seconds hand is the fastest hand of the clock. Observe that it moves very fast, hopping from one number to other.

Seconds hand makes one complete round of the clock in 1 minute.

Time taken by the second's hand to move from one small division to another is called second.

There are 60 equal divisions on a clock face.

Hence,

1 minute = 60 seconds

And 1 hour = 60 minutes

To convert:

  • Minute to second, multiply by 60.
  • Second to minute, divide by 60.

To convert:

  •    Hour to minute, multiply by 60.
  •    Minute to hour, divide by 60.

Example 1: Convert 5 minutes 30 seconds to seconds.

5 minutes 30 seconds = 5 ⨯ 60 seconds + 30 seconds
= 300 seconds + 30 seconds
= 330 seconds

Example 2: Convert 6 hours 55 minutes to minutes.

6 hours 55 minutes = 6 ⨯ 60 minutes + 55 minutes
= 360 minutes + 55 minutes
= 415 minutes.

Example 3: Convert 300 seconds to minutes and seconds.

300 seconds ÷ 60 = 5 minutes

Example 4: : Convert 330 seconds to minutes and seconds.

330 seconds ÷ 60

Q = 5 and R = 30

330 seconds to minutes and seconds = 5 minutes and 30 seconds.

Example 5: Convert 145 minute to hours and minutes.

145 minutes ÷ 60

Q = 2 and R = 25

Therefore, 145 minutes = 2 hours 25 minutes.

Think and Answer

A. Hemant works as a guard at The National Zoological Park, Delhi. Here is his daily routine. Rewrite the sentences by writing the time in a.m. and p.m.

1) He gets up in the morning at 05:00 hours.

2) He has his breakfast at 06:15 hours.

3) He reaches the zoo around 07:00 hours.

4) Opens all the doors at 07:30 hours.

5) Guards the zoo gate from 08:00 hours to 16:00 hours.

6) Locks all the doors at 16:15 hours.

7) Takes a round of the zoo to ensure that no one is left behind at 16:30 hours.

8) Reaches home around 18:00 hours.

Exercise 12.5

A. Convert into seconds.

1. 6 minutes _____________________________________
2. 11 minutes _____________________________________
3. 4 minutes 20 seconds _____________________________________
4. 15 minutes 10 seconds _____________________________________
5. 30 minutes _____________________________________
6. 7 hour 30 minutes _____________________________________

B. Convert into minutes.

1. 12 hours _____________________________________
2. 2 hour 10 minutes _____________________________________
3. 3 hours 15 minutes _____________________________________
4. 4 hours 35 minutes _____________________________________
5. 5 hours 50 minutes _____________________________________
6. 10 hours 10 minutes _____________________________________

C. Convert into minutes and seconds.

1. 180 seconds _____________________________________
2. 350 seconds _____________________________________
3. 570 seconds _____________________________________
4. 800 seconds _____________________________________
5. 1800 seconds _____________________________________
6. 3630 seconds _____________________________________

D. Convert into hours and minutes.

1. 80 minutes _____________________________________
2. 420 minutes _____________________________________
3. 570 minutes _____________________________________
4. 880 minutes _____________________________________
5. 1200 minutes _____________________________________
6. 3600 minutes _____________________________________