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Example 3: Amina started studying at 11:30 a.m. She studied for 2 hours
40 minutes. At what time did she finish studying?
Answer: Time at which Amina started = 11:30 a.m.
11:30 a.m. 1: 30 p.m. 2:10 p.m.
+2 hours +40 mins
Therefore, time at which Amina finished studying
= (duration from 11:30 a.m. to 1:30 p.m.) + (duration from 1:30 p.m. to 2:10)
= 2 hours + 40 minutess
= 2 hours 40 minutes
Example 4: Deepak took 1 hour 40 minutes to complete his maths test. If he
finished at 12:10 p.m., at what time did he start?
Answer: Time at which Deepak finished the maths test = 12:10 p.m.
Converting 12:10 p.m. into 24- hour clock, we have 12:10 hours.
Subtracting 1 hour 40 minutes from 12: 10 hours, we have
Hour Min
11 70
12 10
- 1 40
10 30
Step 1: 10 min < 40 minutes
So borrow 1 hour from 12 hours and change it into minutes.
60 minutes + 10 minutes = 70 minutes
Subtract minutes.
70 minutes – 40 minutes = 30 minutes
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