Chapter- 12
Racing Seconds
Let us find out
1. At what time did Raghav start practising Yoga? ……………….
2. At what time did he finish? …………….
3. How much time did he spend practising Yoga? ....................
4. Find the time elapsed between the given time periods. Share your strategies.
(a) 01:15 p.m. to 01:42 p.m.?
(b) 03:18 p.m. to 08:18 p.m.?
(c) 09:15 a.m. to 11:30 a.m.?
5. The table below shows the time taken by 3 children to paint a picture.
| Name | Time Taken |
|---|---|
| Raghav | 1 hour 20 minutes |
| Rani | 2 hours 10 minutes |
| Ritu | 1 hour 35 minutes |
(a) Who took the longest time?
(b) Who took the least time?
6. Fill in the blanks by writing the time in the appropriate format.
| Time in 12-hour fromat | Time in 24-hour fromat
|
|
|---|---|---|
| 05:30 a.m. | 05:30 hours | |
| ………… | 08:35 hours | |
| 11:55 a.m. | ……… hours | |
| 02:30 p.m. | 14:30 hours | |
| 05:30 p.m. | ……… hours | |
| 09:35 p.m. | ……… hours |
7. Match the following.
| Time in 12–hour format | Time in 24-hour fromat |
|---|---|
| 06:30 a.m. | 01:30 hours |
| 08:45 p.m. | 23:45 hours |
| 11:45 p.m. | 06:30 hours |
| 04:30 a.m. | 20:45 hours |
| 07:30 p.m. | 04:30 hours |
| 01:30 a.m. | 19:30 hours |
School Race
Akira, Sunita, and Mary are participating in a 200 m-walking race.
Do you notice the use of a new unit ‘seconds’ in the picture?
In situations like a race, ‘seconds’ help us observe small differences in 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?
Let Us Do
| Activity | Seconds | Minutes |
|---|---|---|
| Blinking of eyes | ||
| Switching on and switching off the lights | ||
| Counting from 1–20 | ||
| Filling a glass from the tap | ||
| Melting of an ice-cube | ||
| Making a phone call | ||
| Sitting down on the floor | ||
| Drinking a glass of water | ||
| Snapping finger | ||
| Washing hands |
List events other than the ones listed above that you can do or that can happen in less than a minute or in a few seconds.
…………………………………………………………………………
………………………………………
………………………………………
………………………………………
………………………………………
………………………………………
………………………………
Estimate and verify how many of these you can do in a minute.
| Activity | Estimated Number | Actual Number |
|---|---|---|
| Number of balloons blown | ||
| Number of push-ups | ||
| Number of breaths | ||
| Number of hops on one leg |
Let Us Find
1. Find out the number of times you can skip the rope in 10 seconds.
2. How long does it take you to write the word FRIEND?
3. How long does it take you to run 100m?
Let Us Do
Observe the clocks and fill in the blanks.
Draw the missing seconds hand on the clocks on the right side.
Conversion of Hours to Minutes
Zainab and Remo were converting time from hours to minutes and vice-versa.
We know 1 hr = 60 min.
So, 2 hr will have
2 × 60 = 120 min.
Let Us Do
1. Use the double number line below to complete the conversions.
(b) Do as instructed. You can use the above double number line for the following conversions.
(ii) 2 hours 45 minutes = _____ minutes
(iii) 3 hours 15 minutes = _____ minutes
(iv) 4 hours 20 minutes = _____ minutes
(v) 75 minutes = ____ hour ____ minutes
(vi) 150 minutes = ____ hours ____ minutes
(vii) 220 minutes = ____ hours ____ minutes
(viii) 390 minutes = ____ hours ____ minutes
(c) Fill in the blanks in the double number line to complete the conversions.
(ii) 225 sec = ____ min ____ sec
(iii) 700 sec = ____ min ____ sec
(iv) 1,000 sec = ____ min ____ sec
(v) 10 min 13 sec = ____ sec
(vi) 4 min 8 sec = ____ sec
vii) 15 min 40 sec = ____ sec
2. Raghav studies Mathematics, English, Hindi, and The World Around Us subjects. He took 50 minutes to study each of the subjects. Find the total time taken in hours and minutes. Share your strategies with your class.
3. Raghu left his house at 08:00 hours and arrived at his Nana ji’s house at 09:05 hours. How long did he take to reach his house?
08:00 hours to 09:00 hours is
1 hour.
So, Raghu took 1 hour
5 minutes to reach his Nana ji’s
house.
4. Jyoti went to play at 06:15 PM. She came back after 1 hour 45 minutes. At what time did she reach home?
5. Ragini took 1 hour 10 minutes to do her homework. She finished it at 09:40 PM. What time did she start?
6. A group of children left for a picnic at 08:30 AM. They returned after 4 hours and 10 minutes. At what time did they return?
7. Raji started her homework at 06:00 PM. She finished her homework in 1 hour 30 minutes. At what time did she finish?
8. Alya goes out to play at 05:30 PM and comes back after 1 hour 10 minutes. At what time does she come back?
9. If the lunch break of a school starts at 12:30 PM and ends in 35 minutes, what time will lunch end?
10. It is 08:35 PM right now. What time will it be after 8 hours and 25 minutes?