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Answer: 20:15
1 hour = 60 minutes
2 hours = 120 minutes
3 hours = 180 minutes
4 hours = 240 minutes
Using 3 hours = 180 minutes
180 + 45 = 225, so 225 minutes = 3 hours and 45 minutes.
3 hours before midnight is 21:00
45 minutes before 21:00 is 20:15
Using 4 hours = 240 minutes
240 $-$ 15 = 225, so 225 minutes is 15 minutes less than 4 hours.
4 hours before midnight is 20:00
15 minutes after 20:00 is 20:15
24 Hour Conundrum
Age 11 to 14
ShortChallenge Level 
Answer: 20:15
1 hour = 60 minutes
2 hours = 120 minutes
3 hours = 180 minutes
4 hours = 240 minutes
Using 3 hours = 180 minutes
180 + 45 = 225, so 225 minutes = 3 hours and 45 minutes.
3 hours before midnight is 21:00
45 minutes before 21:00 is 20:15
Using 4 hours = 240 minutes
240 $-$ 15 = 225, so 225 minutes is 15 minutes less than 4 hours.
4 hours before midnight is 20:00
15 minutes after 20:00 is 20:15
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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