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Example 2: Subtract the following:
( a) 48 minutes 34 seconds from 54 minutes 20 seconds

( b) 7 hours 54 minutes from 13 hours 22 minutes
Solution:

( a) Step 1: Subtract seconds:
There are not enough seconds.

So, regroup minutes and seconds. min s
53 80
54 minutes 20 seconds = 53 minutes 80 seconds 54 20
Now, 80 seconds – 34 seconds = 46 seconds. – 48 34

Step 2: Subtract minutes: 5 46
53 minutes – 48 minutes = 5 minutes

Thus, 54 minutes 20 seconds – 48 minutes 34 seconds
= 5 minutes 46 seconds.

( b) Step 1: Subtract minutes:
There are not enough minutes.
h
So, regroup hours and minutes. 12 min
82
13 hours 22 minutes = 12 hours 82 minutes 13 22
Now, 82 minutes – 54 minutes = 28 minutes. – 7 54

Step 2: Subtract hours: 5 28
12 hours – 7 hours = 5 hours

Thus, 13 hours 22 minutes – 7 hours 54 minutes = 5 hours 28 minutes.

Example 3: What time will it be at 3 hours 40 minutes after 6:30 p.m.?
Solution: h min
1
Step 1: Convert 6:30 p.m. into the 24-hour clock. 18 30
6:30 p.m. = 1830 hours = 18 hours 30 minutes + 3 40

Step 2: Add 3 hours 40 minutes and 18 hours 30 minutes. 22 10
Š 30 minutes + 40 minutes = 70 minutes

70 minutes = 60 minutes + 10 minutes = 1 hour + 10 minutes
Š 1 hour + 18 hours + 3 hours = 22 hours

Thus, required time = 22 hours 10 minutes = 2210 hours = 10:10 p.m.

Example 4: Subtract 18 years 9 months from 23 years. years Months
Solution: We have: 23 years = 23 years 00 months 22 12

= 22 years 12 months – 23 00
18
09
and 18 years 9 months = 18 years 09 months 4 03
Required difference = 4 years 3 months

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