Racing Seconds Chapter Notes | Mathematics (Maths Mela) Class 5 - New NCERT PDF Download

Time helps us know when things happen and how long they take. We measure time in seconds, minutes, and hours. Seconds are for very short moments, minutes for small tasks, and hours for bigger activities. Clocks and watches help us read and keep track of time in our daily lives.

Measuring Time

We measure time in seconds, minutes, and hours.

Seconds

• A second is the smallest unit of time we commonly use.
• It is very short, like the time it takes to blink your eyes, snap your fingers, or say “go!”
• 60 seconds = 1 minute.

Minutes

• A minute is longer than a second and is used for small tasks.
• Examples include tying your shoelaces, sipping a glass of water, or reading a short paragraph in a book.
• 1 minute = 60 seconds.

Hours

• An hour is a longer period of time made up of 60 minutes.
• It can be used to measure bigger activities like watching a cartoon, playing outside with friends, or finishing a short homework assignment.
• 1  hour = 60 minutes = 3,600 seconds.

Let us Do

Estimate whether you would take seconds or minutes to complete the following activities. Tick the appropriate cell.

Sol: 

Conversion of Time Units

1. Seconds → Minutes

• 60 seconds = 1 minute
• To change seconds into minutes, divide by 60.
• Example:
  • 120 seconds ÷ 60 = 2 minutes
  • 150 seconds ÷ 60 = 2 minutes 30 seconds

2. Minutes → Seconds

• 1 minute = 60 seconds
• To change minutes into seconds, multiply by 60.
• Example:
  • 5 minutes × 60 = 300 seconds
  • 2 minutes 15 seconds = (2 × 60) + 15 = 135 seconds

3. Minutes → Hours

• 60 minutes = 1 hour
• To change minutes into hours, divide by 60.
• Example:
  • 180 minutes ÷ 60 = 3 hours
  • 150 minutes ÷ 60 = 2 hours 30 minutes

4. Hours → Minutes

• 1 hour = 60 minutes
• To change hours into minutes, multiply by 60.
• Example:
  • 2 hours × 60 = 120 minutes
  • 3 hours 45 minutes = (3 × 60) + 45 = 225 minutes

5. Hours → Seconds

• 1 hour = 3,600 seconds
• Multiply the hours by 3,600.
• Example:
  • 2 hours × 3,600 = 7,200 seconds

6. Seconds → Hours

• 3,600 seconds = 1 hour
• Divide seconds by 3,600.
• Example:
  • 7,200 seconds ÷ 3,600 = 2 hours
  • 5,400 seconds ÷ 3,600 = 1 hour 30 minutes

School Race 

• Time duration means how long something lasts.
• It is found by checking the start time and the end time.
• Example: A football match starts at 1:15 p.m. and ends at 1:42 p.m..
  From 1:15 to 1:42 is 27 minutes. That is the time duration of the match.

Akira, Sunita, and Mary are participating in a 200 m walking race

Do you notice the use of the unit, ‘seconds’, in the picture?

In situations like a race, ‘seconds’ help us observe small differences in the time taken by participants. 

Each participant took 1 minute, but how much more? Identify the child who won the race. How much time did the child take?

Sol:  The child who won the race is the one standing in the first place podium — she took 1 minute 55 seconds to complete the 200 m walking race. In races, even a difference of 1 second can change the winner, which is why seconds are used along with minutes to measure time precisely.

Mastering the Clock

• A clock usually has three hands - the hour hand, the minute hand, and the second hand. 
• The hour hand is short and shows the hour.
• The minute hand is long and shows the minutes. 
• The second hand is thin and moves quickly to show the seconds.

How to read time using a clock:

1. Look at the hour hand first and see which number it is pointing to or between.
2. Check the minute hand next. Each big number on the clock represents 5 minutes. For example, if the minute hand is on “3,” it means 15 minutes past the hour.
3. Check the seconds hand if needed. Like the minute hand, each number represents 5 seconds, and one full round of the seconds hand is 60 seconds or 1 minute.

Example:

Let us perform an activity:

Raghav practices yoga in the morning.

Let us find out

1. At what time did Raghav start practising Yoga? ……………….
Ans: The clock shows the short hand (hour hand) between 5 and 6, and the long hand (minute hand) on 7.
That means the time is 5:35 a.m.
2. At what time did he finish? …………….
Ans: The second clock shows the short hand near 6 and the long hand on 11. That means the time is 6:55 a.m.
3. How much time did he spend practising Yoga? ....................
Ans: Start time = 5:35 a.m.
End time = 6:55 a.m.
Time taken = 20 minutes.
4. Find the time elapsed between the given time periods. Share your strategies. 
(a) 01:15 p.m. to 01:42 p.m.?
→ 42 minutes − 15 minutes = 27 minutes.
(b) 03:18 p.m. to 08:18 p.m.?
→ 8 hours 18 minutes − 3 hours 18 minutes = 5 hours.
(c) 09:15 a.m. to 11:30 a.m.?
→ Hours: 11 − 9 = 2 hours.
Minutes: 30 − 15 = 15 minutes.
Total = 2 hours 15 minutes.
5. The table below shows the time taken by 3 children to paint a picture.

(a) Who took the longest time?
Ans: Rani (2 hours 10 minutes)
(b) Who took the least time?
Ans: Raghav (1 hour 20 minutes)

Converting Time Formats

• Time can be written in two formats – the 12-hour format and the 24-hour format.
• Both show the same time of day, but they use a different style of writing

12-hour format

• The clock numbers go from 1 to 12 and then repeat.
• To show morning or evening, we use a.m. and p.m.
• a.m. means before midday (from 12:00 midnight to 11:59 a.m.).
• p.m. means after midday (from 12:00 noon to 11:59 p.m.).
• Example: 05:30 a.m. = morning, 02:30 p.m. = afternoon.

24-hour format

• The clock counts time continuously from 00:00 to 23:59.
• There is no a.m. or p.m. because the hour number itself shows the time of day.
• Morning times are written the same, with two digits for hours (e.g., 5:30 a.m. → 05:30 hours).
• For afternoon and evening, we add 12 to the hour (e.g., 2:30 p.m. → 14:30 hours, 11:45 p.m. → 23:45 hours).

Let us perform an activity:

1. Fill in the blanks by writing the time in the appropriate format.

Sol:

2. Match the following.

Sol: