Page 242 - New Medley 5 Semester 1

Solution: Start addition from smaller units and move to the bigger
ones. If required, regroup the units from the smaller to

bigger.

(a) 6 h 15 min 26 s Regroup Regroup

+ 5 h 25 min 24 s +1 +1

11 h 40 min 50 s = 29 h (60 + 3) min (60 + 10)s
= 30 h 4 min 10 s
(b) 15 h 38 min 30 s

+ 14 h 25 min 40 s

29 h 63 min 70 s

Example 5: Subtract the following:

(a) 8 h 16 min 24 s from 20 h 30 min 40 s

(b) 12 h 48 min 55 s from 20 h 25 min 35 s

Solution: Subtract seconds from seconds, minutes from minutes and

hours from hours. If needed, borrow from the bigger units
and subtract after regrouping.
84

19 24 95
(a) 20 h 30 min 40 s (b) 20 h 25 min 35 s

– 8 h 16 min 24 s – 12 h 48 min 55 s

12 h 14 min 16 s 7 h 36 min 40 s

Example 6: (a) Multiply 3 h 12 min 15 s by 8.

(b) Multiply 2 weeks 4 days 8 hours by 3.

Solution: (a) Start multiplication from the smaller units and regroup

the product into the bigger units.

h min s
3 12 15
= 24 h 98 min 0 s ( 120 s = 2 min)
× 8
= 25 h 38 min ( 60 min = 1 h)
24 96 120

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