Back to: Mathematics Primary 6
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In previous classes, we would have learnt how to tell time. In this lesson, we will be learning conversion of time.
60 secs = 1 minute
60 mins = 1 hour
24 hours = 1 day
7 days = 1 week
4 weeks = 1 month
12 months = 1 year
52 weeks = 1 year
365 days = 1 year
366 days = 1 leap year
Examples:
- How many minutes in 6 hours?
1 hour = 60 minutes. So, 6 hours = (6 × 60) minutes. = 360 minutes.
- Convert 220 minutes to hours and minutes. 60 minutes = 1 hour
220 minutes = (220/60) hours
= 3 hours 40 minutes.
Activity
- 1. Convert the following:
(i) 7 days 6 hours into hours.
(ii) 6 hours 40 minutes into minutes.
(iii) 4 minutes 25 seconds into seconds.
- Convert the following:
(i) 5 years 9 months into months.
(ii) 4 months 10 days into days.
(iii) 7 weeks 6 days into days.
(iv) 1 year into seconds.
- Convert the following:
(i) 80 months into years and months.
(ii) 210 weeks into years and weeks.
(iii) 530 days into weeks and days.
Addition and Subtraction of Time
Example 1 :What is 2:45 + 1:10 ?
Solution: Add the Hours: 2+1 = 3
Add the Minutes: 45+10 = 55
The minutes are OK, so the answer is 3:55
Example 2: What is 2:45 + 1:20? Add the Hours: 2+1 = 3 Add the Minutes: 45+20 = 65
The minutes are 60 or more, so
subtract 60 from minutes (65−60 = 5 Minutes)
and add 1 to Hours (3+1 = 4 Hours) so the answer is 4:05
Example 3: What is 4:10 – 1:05?
Subtract the Hours: 4−1 = 3
Subtract the Minutes: 10−5 = 5
The minutes are OK, so the answer is 3:05
Example 4: What is 4:10 – 1:35? Subtract the Hours: 4−1 = 3
Subtract the Minutes: 10−35 = −25
The minutes are less than 0, so:
add 60 to Minutes (−25+60 = 60−25 = 35 Minutes)
and subtract 1 from Hours (3−1 = 2 Hours) The answer is 2:35
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