# Math in Focus Grade 3 Chapter 16 Practice 5 Answer Key Elapsed Time

This handy Math in Focus Grade 3 Workbook Answer Key Chapter 16 Practice 5 Elapsed Time provides detailed solutions for the textbook questions.

## Math in Focus Grade 3 Chapter 16 Practice 5 Answer Key Elapsed Time

Tell what time it will be.

Question 1.
2 hours after 8:00 P.M. _____________
Explanation:
By using a timeline we can calculate elapsed time:
2 hours after 8:00 PM means if we add 8 and 2 then we get 8+2=10 hours.

1. The start time and end times are labelled on an end of a timeline.
2. Between 8:00 and 10:00 are the hours of 9:00, which are marked on the timeline.
3. Between 8:00 and 10:00 there are 2 hours.

Question 2.
3 hours before 6:40 A.M. ______________
Explanation:
1. Calculating the elapsed time means finding the difference between two times.
2. To calculate the elapsed time, it is easiest to count up in hours.
3. Here asked 3 hours before the given time. So we need to subtract 6:40 And 3 hours then we get 6:40-3:00=3:40.
4. The elapsed time is 3 hours 40 minutes A.M.

Question 3.
30 minutes after 1:36 P.M. _______________
Explanation:

1. The start time and end times are labelled on an end of a timeline.
2. Between 1:36 and 2:01 are the hours of 2:00, which are marked on the timeline.
3. We subtract the 36 minutes of 1:36 from the 60 minutes to get 24 minutes. There are 24 minutes from 1:36 pm and 2:00 pm.
4. Between 1:36 pm and 1:40 there are 4 minutes.
5. Between 1:40 pm and 2:00 pm there are 25 minutes.
6. We need to calculate for 30 minutes. And from 2:00 pm to 2:01 pm, there is 1 minute.
7. Now adding all the minutes, 4 +25+1=30.
8. Finally, 1:36 pm after 30 minutes are 2:01 pm.

Question 4.
45 minutes before 7:05 A.M. _____________
Here given end time that is 7:05 AM. We need to calculate the start time.

Explanation:
1. Now I calculated the start time by using the given 45 minutes.
2. First I wrote 7:05 AM on the timeline as an end date. From there I started counting start times.
3. Then I take the earliest time to 7:05 AM that is 7:00 AM. Between both timings, there are 5 minutes.
4. And then I take 6:30 AM which is nearer to 7:00 AM. Between both timings, there are 30 minutes.
5. And we need to calculate for extra 10 minutes. From 6:30 to 6:20 there are 10 minutes so I took 6:20 AM.
6. Now add all the minutes 5+30+10=45 minutes.
7. The start time is 6:20 AM.

Question 5.
3 hours after 1 0:25 A.M. ______________
Explanation:

Explanation:
1. Now I calculated the end time.
2. I wrote the start time on the timeline that is 10:25 AM.
3. I subtracted the 25 minutes of 10:25 AM from the 60 minutes to get 35 minutes. There are 35 minutes from 10:25 am and 11:05 am.
4. Between 11:05 am and 12:05 pm there is 1 hour.
5. Between 12:05 to 1:05 PM there is 1 hour.
6. Between 1:05 Pm to 1:30 Pm there is 25 minutes.
7. add all the hours1 hour+1 hour=2 hours.
8. Now add minutes 35 min+25 min=60 min which is equal to 1 hour.
9. Finally, 3 hours. The 10:25 after 3 hours is 1:30 PM.

Question 6.
2 hours before 1:20 P.M. ______________
Explanation:

1. Already given end time that is 1:20 PM. We need to calculate the start time means before 2 hours.
2. We subtracted 20 min of 1:20 PM from the 60 minutes to get 40 min. So we calculated the difference of 40 min we get the time of 12:35 PM.
3. We calculated for 20 min because from their 1 hour will be completed. So we had taken 12:15. From 12:15 to 12:35 there is 1 hour.
4. And from 12:15 Pm to 11:15 AM there is 1 hour.
5. Finally we calculated for 2 hours. The start time is 11:15 AM.

Example

Question 7.
7:45 P.M. to 8:15 P.M. _____________
Explanation:

1. The start time and end times are labelled at the end of the timeline.
2. Between 7:45 PM and 8:15 PM are the hours of half an hour which is marked on the timeline.
3. We subtract the 45 min of 7:45 PM from the 60 min to get 15 min. There are 15 minutes from 7:45 PM to 8:00 PM.
4. From 8:00 PM to 8:15 PM there are 15 minutes.
5. We add the minutes together. 15+15=30 minutes.
6. The elapsed time is 30 minutes.

Question 8.
2:30 P.M. to 4:50 P.M. _______________
Explanation:

1. The start time and end times are labelled at the end of the timeline.
2. Between 2:30 PM and 4:50 PM are the hours of 3:00 and 4:00 PM which are marked on the timeline.
3. We subtract 30 min of 2:30 from the 60 min to get 30 min. There are 30 minutes from 2:30 and 3:00 PM.
4. Between 3:00 and 4:00 there is 1 hour.
5. Between 4:00 and 4:50 there are 50 minutes.
6. Adding minutes together. 30+50=80. Such that, we already know, 1 hour=60 minute. So, we can say 80 minutes is nothing but 1 hour 20 minutes.       (80-60=20)
7. Now by adding hours 1+1=2 hours.
8. Hence the resultant is 2 hour 20 minutes.

Question 9.
7:45 A.M. to 9:50 A.M _______________
Explanation:

1. The start time and end times are labelled at the end of the timeline.
2. Between 7:45 AM and 9:50 AM are the hours of 8:00 and 9:00 AM which are marked on the timeline.
3. We subtract 45 min of 7:45 from the 60 min to get 15 min. There are 15 minutes from 7:45 and 8:00 AM.
4. Between 8:00 and 9:00 there is 1 hour.
5. Between 9:00 and 9:50 there are 50 minutes.
6. Adding minutes together. 15+50=65. Such that, we already know, 1 hour=60 minute. So, we can say 80 minutes is nothing but 1 hour 5 minutes.       (65-60=5)
7. Now by adding hours 1+1=2 hours.
8. Hence the resultant is 2 hours 5 minutes.

Question 10.
11:30 P.M. to 2:10 A.M. _______________

Explanation:
1. The start time and end times are labelled at the end of the timeline.
2. Between 11:30 PM and 2:10 AM are the hours of 12:00, 1:00, 2:00 AM which are marked on the timeline.
3. We subtract 30 min of 11:30 from the 60 min to get 30 min. There are 30 minutes from 11:30 and 12:00 AM.
4. Between 12:00 and 1:00 there is 1 hour.
5. Between 1:00 and 2:00 there is 1 hour.
6. Between 2:00 and 2:10 there are 10 minutes.
8. Now by adding hours 1+1=2 hours.
9. Hence the resultant is 2 hours 40 minutes.

Question 11.
11:25 A.M. to 3:10 P.M. _______________
Explanation:

1. The start time and end times are labelled at the end of the timeline.
2. Between 11:25 AM and 12:00 PM are the hours of 12:00, 1:00, 2:00, 3:00 PM which are marked on the timeline.
3. We subtract 25 min of 11:25 from the 60 min to get 35 min. There are 35 minutes from 11:25 and 12:00 PM.
4. Between 12:00 and 1:00 there is 1 hour.
5. Between 1:00 and 2:00 there is 1 hour.
6. Between 2:00 and 3:00 there is 1 hour.
7. Between 3:00 and 3:10 there are 10 minutes
8. Now by adding hours 1+1+1=3 hours.
9. Hence the resultant is 3 hours 45 minutes.

Write the correct time. Draw the missing hands on each clock.

Question 12.

1. Start time is given and need to calculate the end time.
2. 3 hours 15 minutes after the time is 12:45.
3. From 9:30 PM to 10:30 Pm there is 1 hour.
4. Between 10:30 PM to 11:30 Pm there is 1 hour.
5. Between 11:30 to 12:30 PM there is 1 hour.
6. Between 12:30 to 12:45 there is 15 minutes.
7. Adding hours we get 1+1+1=3 hours.
8. The minutes are 15 minutes.
9. Hence resultant is 3 hours 15 minutes that is 12:45.

Question 13.

Explanation:
1. We already know the end time that is 2:00 AM
2. We need to calculate the elapsed time, 2 hours and 45 minutes.
3. Between 2:00 to 1:00 there is 1 hour.
4. Between 1:00 to 12:00 there is 1 hour.
5. 12:00 to 11:15 there are 45 minutes.
6. So I had taken 11:45 PM for 12:00 AM to 45 minutes.

Question 14.
Suki exercises every morning. She starts at 6:30 A.M. and ends at 8:15 A.M. How long does she exercise?

Starting time=6:30 AM
Ending time=8:15 AM

1. The start time and end times are labelled at the end of the timeline.
2. Between 6:30 AM and 8:15 AM are the hours of 7:00, 8:00 AM which are marked on the timeline.
3. We subtract 30 min of 6:30 from the 60 min to get 30 min. There are 30 minutes from 6:30 and 7:00 AM.
4. Between 7:00 and 8:00 there is 1 hour.
5. Between 8:00 and 8:15 there is 15 minutes.
9. Hence the resultant is 1 hour 45 minutes.
Explanation:

Question 15.
Devon started reading a book at 2:35 P.M. She took 3 hours 10 minutes to finish the book. What time did she finish reading the book?

Starting time=2:35 PM
Ending time=X
The given time=3 h 10 min.

Explanation:
1. The start time is labelled on the timeline that is 2:35 PM
2. Subtract 35 minutes of 2:35 from 60 minutes to get 25 min. There is 25 min from 2:35 and 3:00 PM.
3. From there we need to calculate 3 h 10 min after time.
4. Start from 3:00 PM, between 3:oo PM to 4:00 PM there is 1 hour.
5. Between 4:00 PM to 5:00 PM there is 1 hour.
6. Between 5:00 PM to 5:35 PM there are 35 minutes.
7. Between 5:35 to 5:45 there are 10 minutes.
8. Likewise we need to calculate the ending time.
9. Adding all the minutes:25+35+10=70 minutes. We can write 70 as 1 hour 10 minutes. (1 hour=60 minutes).
10. Finally, the result of 3 h 10 min is 5:45 PM.

Question 16.
Lissa went to the library. She was there for 2 hours 15 minutes. She left the library at 5:40 P.M. What time did she get to the library?
We need to calculate starting time.
We can say it as another way 2 hours 15 minutes before 5:40 PM.

Explanation:
1. The end time is labelled on the timeline that is 5:40 PM
2. Subtract 40 min of 5:40 from 60 min to get 20. The 20 min before 5:40 is 5:20 PM.
3. Now calculate for 1 hour that is 5:20 to 4:20.
4. Now we need to calculate for 55 minutes. The 55 minutes before 4:20 is 3:25 PM.

Question 17.
Marcus visited his friend’s house from 11:50 A.M. to 3:15 P.M. How long was his visit?

Starting time=11:50 AM
Ending time=3:15 PM

1. The start time and end times are labelled at the end of the timeline.
2. Between 11:50 AM and 12:00 PM are the hours of 12:00, 1:00, 2:00, 3:00 PM which are marked on the timeline.
3. We subtract 50 min of 11:50 from the 10 min to get 10 min. There are 10 minutes from 11:50 and 12:00 PM.
4. Between 12:00 and 1:00 there is 1 hour.
5. Between 1:00 and 2:00 there is 1 hour.
6. Between 2:00 and 3:00 there is 1 hour.
7. Between 3:00 and 3:15 there are 15 minutes
8. Now by adding hours 1+1+1=3 hours.
9. Hence the resultant is 3 hours 25 minutes.

Question 18.
Mr. Nelson took 3 hours 30 minutes to decorate his classroom. He started at 9:20 A.M. What time did he finish?

Starting time=9:20 AM
The elapsed time is given: 3 h 30 min.
Ending time=X

Explanation:
1. I labelled starting time on the timeline that is 9:20 AM
2. Subtract 20 min of 9:20 from the 60 min to get 60-20=40.
4. And from there, calculate according to the elapsed time.
5. Now calculate for 3 hours and then calculate for 30 minutes.
6. Now observe the above timeline in which we represented all the calculations.
7. Finally, the end time is 12:45 PM.

Question 19.
Mrs Martin’s flight landed at 2:25 A.M. The flight was 4 hours 45 minutes long. What time did the flight take off?

Starting time=2:25 AM
Elapsed time=4 h 45 min
Ending time=X

Explanation:
1. I labelled starting time on the timeline that is 2:25 AM
2. Subtract 25 min of 2:25 from the 60 min to get 60-25=35.
4. And from there, calculate according to the elapsed time.
5. Now calculate for 4 hours and then calculate for 1o minutes because we calculated already 35 minutes.
6. Now observe the above timeline in which we represented all the calculations.
7. Finally, the end time is 7:10 AM.