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

Page No. 155

Raghav practices yoga in the morning.

Let us find out

Q1: At what time did Raghav start practising Yoga?
Ans:
Raghav started practicing Yoga at 05:35 a.m.

Q2: At what time did he finish?
Ans:
Raghav finished at 05:55 a.m.

Q3: How much time did he spend practising Yoga?
Ans:
He started at 05:35 a.m. and
finished at 05:55 a.m.

Since, 55 – 35 = 20

So, he spent 20 minutes practicing Yoga.

Q4: Find the time elapsed between the given time periods. Share your strategies.
(а) 01:15 p.m. to 01:42 p.m.?
Ans:
Time elapsed between 01:15 p.m. to 01: 42 p.m. = 27 minutes

(b) 03:18 p.m. to 08:18 p.m.?
Ans:
Time elapsed between 03:18 p.m. to 08:18 p.m. = 5 hours

(c) 09:15 a.m. to 11:30 a.m.?
Ans:
Time elapsed between 09:15 a.m. to 11:30 a.m.
= 2 hours 15 minutes.

Q5: The table below shows the time taken by 3 children to paint a picture.

(а) Who took the longest time?
(b) Who took the least time?
Ans:
(a) Since, 2 hours 10 minutes > 1 hours 35 minutes > 1 hour 20 minutes
So, Rani took the longest time.

(b) Raghav took the least time.

Page No. 156-158

Q6: Fill in the blanks by writing the time in the appropriate format.
Ans:

Q7:
Ans:

School Race

Akira, Sunita, and Mary are participating in a 200 m-walking race.
Q: Do you notice the use of a new unit ‘seconds’ in the picture?
1 min = 60 seconds
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?
Ans:
The child who won the race is encircled.
She took 1 minute 55 seconds.

Let us Do

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

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.
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
Ans:
Do it yourself.

Estimate and verify how many of these you can do in a minute.
Ans:
Do it yourself.

Let Us Find

Q1: Find out the number of times you can skip the rope in 10 seconds.
Ans:
Do it yourself.

Q2: How long does it take you to write the word FRIEND?
Ans:
Do it yourself.

Q3: How long does it take you to run 100m?
Ans:
Do it yourself.

Page No. 159 -160

Let Us Do

Observe the clocks and fill in the blanks.

Q1: Rani took __________ sec. to get out of her bed.
Ans:
Rani took 30 sec. to get out of her bed.

Q2: Raghav took ________ sec. to move from his room to the kitchen.
Ans:
Raghav took 35 sec. to move from his room to the kitchen.

Q3: Ritu took ________ sec. to pick up a piece of paper from the floor.
Ans:
Ritu took 15 sec. to pick up a piece of paper from the floor.

Q4: Raghu took ________ sec. to wash his spoon and plate.
Ans:
Raghu took 60 sec. to wash his spoon and plate.

Q: Draw the missing seconds hand on the clocks on the right side.
Ans:
Do it yourself.

Page No. 161 -163

Let Us Do

Q1: Use the double number line below to complete the conversions.
Ans:
(a) 1 hr = 60 min
2 hr = 2 × 60 = 120 min
4 hr = 4 × 60 = 240 min
7 hr = 7 × 60 = 420 min
480 min = 8 hr

As, 8 hr = 8 × 60 = 480 min
9 hr = 9 × 60 = 540 min
660 min = 11 hr

As, 11 hr = 11 × 60 = 660 min
720 min = 12 hr

As, 12 hr = 12 × 60 = 720 m

(b) Do as instructed. You can use the above double number line for the following  conversions.
Ans:
(i) 1 hr 10 min = 60 min + 10 min = 70 min
So, 1 hour 10 minutes = 70 minutes.

(ii) 2 hr 45 min = 120 min + 45 min = 165 min
So, 2 hours 45 minutes = 165 minutes,

(iii) 3 hr 15 min = 3 times 60 + 15 min – 180 min + 15 min = 195 min
So, 3 hours 15 minutes = 195 minutes.

(iv) 4 hr 20 min = 4 times 60 + 20 min
= 240 min + 20 min = 260 min
So, 4 hours 20 minutes = 260 minutes.

(v) 75 min = 60 min + 15 min = 1 hr 15 min
So, 75 minutes = 1 hour 15 minutes.

(vi) 150 min = 120 min + 30 min = 2 hr 30 min
So, 150 minutes = 2 hours 30 minutes.

(vii) 220 min = 120 min + 60 min + 40 min = 2 hr + 1 hr + 40 min = 3 hr 40 min
So, 220 minutes = 3 hours 40 minutes.

(viii) 390 min = 240 min + 120 min + 30 Mn = 4 hr + 2 hr + 30 min = 6 hr + 30 min
So, 390 minutes = 6 hours 30 minutes

(c) Fill in the blanks in the double number line to complete the conversions.
Ans:
120 sec = 2 min, as 2 min = 2 × 60 = 120 sec.
Multiplying by 5 to the previous marking we get the number for the next marking on the number line for minutes. To get the corresponding seconds on the seconds number line we need to multiply the number of minutes by 60.
(i) 320 sec = 300 sec + 20 sec = 5 min + 20 sec
So, 320 sec = 5 min 20 sec

(ii) 225 sec = 120 sec + 60 sec + 45 sec
= 2 min + 1 min + 45 sec
So, 225 sec = 3 min 45 sec

(iii) 700 sec = 600 sec + 60 sec + 40 sec
= 10 min + 1 min + 40 sec
So, 700 sec = 11 min 40 sec

(iv) 1000 sec = 900 sec + 60 sec + 40 sec
= 15 min + 1 min + 40 sec
So, 1000 sec = 16 min 40 sec

(v) 10 min 13 sec = 600 sec + 13 sec
= 613 sec
So, 10 sec 13 sec = 613 sec

(vi) 4 min 8 sec = 2 min + 2 min + 8 sec
= 120 sec + 120 sec + 8 sec = 248 sec
So, 4 min 8 sec = 248 sec

(vii) 15 min 40 sec = 900 sec + 40 sec
= 940 sec
So, 15 min 40 sec = 940 sec

Q2: 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.
Ans:
Raghav studies total 4 subject.
He took 50 minutes for each.
So, total time taken = 50 × 4 = 200 min
Now, 200 min = 180 min + 20 min
= 3 × 60 min + 20 min = 3 hr 20 min
Thus, total time taken = 3 hours 20 minutes.

Q3: 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?
Ans: Do it yourself.

Q4: Jyoti went to play at 06:15 PM. She came back after 1 hour 45 minutes. At what time did she reach home?
Ans:
1 hour after 06:15 PM is 07:15 PM and 45 minutes after 07:15 PM is 07:60 PM that is, 08:00 PM.
So, 1 hour 45 minutes after 06:15 PM is 08:00 PM.
Therefore, Jyoti reached home at 08:00 PM.

Q5: Ragini took 1 hour 10 minutes to do her homework. She finished it at 09:40 PM. What time did she start?
Ans:
1 hour before 09:40 PM is 08:40 PM and 10 minutes before 08:40 pm is 08:30 PM.
So, 1 hour 10 minutes before 09:40 PM is 08:30 PM.
Therefore, Ragini started her homework at 08:30 PM.

Q6: 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?
Ans:
4 hours after 08:30 AM is 12:30 PM, and 10 minutes after 12:30 PM is 12:40 PM. So, 4 hours 10 minutes after 08:30 AM is 12:40 PM.
Therefore, the children returned at 12:40 PM.

Q7: Raji started her homework at 06:00 PM. She finished her homework in 1 hour 30 minutes. At what time did she finish?
Ans:
1 hour 30 minutes after 06:00 PM is 07:30 PM. So, Raji finished her homework at 07:30 PM.

Q8: Alya goes out to play at 05:30 PM and comes back after 1 hour 10 minutes. At what time does she come back?
Ans:
1 hour after 05:30 PM is 06:30 PM, and 10 minutes after 06:30 PM is 06:40 PM.
So, Alya came back at 06:40 pm.

Q9: If the lunch break of a school starts at 12:30 PM and ends in 35 minutes, what time will lunch end?
Ans:
35 minutes after 12:30 PM is 12:65 PM that is 01:05 PM (As, 65 minutes = 1 hr 5 min)
So, the lunch will end at 01:05 PM.

Q10: It is 08:35 PM right now. What time will it be after 8 hours and 25 minutes?
Ans:
4 hours after 08:35 PM is 00:35 AM, and 4 hours after 00:35 AM is 04:35 AM, and 25 minutes after 04:35 AM is 04:60 AM, that is 05:00 AM.
Thus, 8 hours 25 minutes after 08:35 PM is 5:00 AM.