High School

4. Write down the digital time:

a) 1 hour after 4 pm

b) 3 hours before 2 am

c) 2 hours 30 minutes before 4:30 am

d) 1 hour 20 minutes before 9 am

5. If you are 500,000,000 seconds old, how old are you in years, days, hours, minutes, and seconds? Take one year as 365 days.

6. An aeroplane departs from Port Elizabeth at 13:15 and arrives at Johannesburg at 14:55. How long does the flight take?

7. Thapelo takes 3 hours, 4 minutes, and 12 seconds to complete his homework. Sophie takes 2 hours, 50 minutes, and 25 seconds to complete her homework. If they start at the same time, how long before Thapelo does Sophie finish her homework?

Answer :

  1. Let's find the digital time for each part:

    a) 1 hour after 4 PM:

    • 4 PM is the same as 16:00 in 24-hour time.
    • 1 hour after 16:00 is 17:00.
    • So, 1 hour after 4 PM is 5:00 PM.

    b) 3 hours before 2 AM:

    • 2 AM is the same as 02:00 in 24-hour time.
    • 3 hours before 02:00 is 23:00 (from the previous day).
    • So, 3 hours before 2 AM is 11:00 PM.

    c) 2 hours 30 minutes before 4:30 AM:

    • 4:30 AM is the same as 04:30 in 24-hour time.
    • Subtract 2 hours and 30 minutes from 04:30:
      04:30 - 2:00 = 02:30, and then 02:30 - 0:30 = 02:00.
    • So, 2 hours 30 minutes before 4:30 AM is 2:00 AM.

    d) 1 hour 20 minutes before 9 AM:

    • 9 AM is the same as 09:00 in 24-hour time.
    • Subtract 1 hour and 20 minutes from 09:00:
      09:00 - 1:00 = 08:00, and then 08:00 - 0:20 = 07:40.
    • So, 1 hour 20 minutes before 9 AM is 7:40 AM.

  2. Let's calculate how old you are if you are 500,000,000 seconds old:

    • There are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a day.
    • You'll first convert seconds into minutes: 500,000,000 seconds [tex]\div[/tex] 60 = 8,333,333.33 minutes.
    • Then into hours: 8,333,333.33 minutes [tex]\div[/tex] 60 = 138,888.89 hours.
    • Then into days: 138,888.89 hours [tex]\div[/tex] 24 = 5787.04 days.
    • Then into years: 5787.04 days [tex]\div[/tex] 365 = 15.86 years.
    • This means you are approximately 15 years, 287 days old.

  3. To find out how long the flight takes from Port Elizabeth to Johannesburg:

    • Departure time is 13:15.
    • Arrival time is 14:55.
    • To find the duration, subtract the departure time from the arrival time:
      14:55 - 13:15 = 1 hour and 40 minutes.
    • So, the flight takes 1 hour and 40 minutes.

  4. To find how long before Thapelo does Sophie finish her homework:

    • Thapelo's time: 3 hours, 4 minutes, 12 seconds.
    • Sophie's time: 2 hours, 50 minutes, 25 seconds.
    • Calculate the difference:
      • Hours: 3 - 2 = 1 hour.
      • Minutes: 4 - 50 = -46 (Borrow 1 hour as 60 minutes: 60 - 50 = 10 minutes).
      • Seconds: 12 - 25 = -13 (Borrow 1 minute as 60 seconds: 60 - 25 = 35 seconds).
    • Total difference = 1 hour - 10 minutes - 47 seconds.
    • Sophie finishes 13 minutes and 47 seconds before Thapelo.

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