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Dr. Keh-Gong Shih
Figure 701 : Clock - Angle between two hands
Q01 |
- Diagram : Clock - Angle between two hands
Q02 |
- Angle of short hand
Q03 |
- Angle of minute hand
Q04 |
- Time when hour hand and minute hand coincide
Q05 |
- Angle of hour hand when hour hand and minute hand coincide
Q01. Diagram : Angle between two hands
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Q02. Angle of hour hand
Definition
Each hour = 360 degrees/12
Angle of hour hand relative to 12 o'clock
1 o'clock = 30 degrees
2 o'clock = 60 degrees
3 o'clock = 90 degrees
4 o'clock = 120 degrees
5 o'clock = 150 degrees
6 o'clock = 180 degrees
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Q03. Angle of minute hand
Definition
Each minute = 360 degrees/60 = 6 degrees
Angle of minute hand relative to 12 o'clock position
At 1 minute = 6 degrees
At 15 minute = 90 degrees
At 30 minute = 180 degrees
At 45 minute = 270 degrees
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Q04. Angle between two hands
Time of short hand when two hands coincide between 3 and 4 o'clock
Let hour = x
Let minute = y
The time is x + y/60
Hence angle of short hand = (x + y/60)*30
Hence angle of minute hand = 6*y
Since two hands are coincided
Hence (x + y/60)*30 = 6*y
Hence y = 30*x/(6 - 0.5)
Between 3 and 4 o'clock, x = 3
Hence y =90/5.5 = 16.3636 minutes
Hence the time is 3 o'clock 16.36 minutes
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Q05. Angle of hour hand when hour hand and minute hand coincide
Angle of short hand when two hands coincide between 3 and 4 o'clock
Let hour = x
Let minute = y
The time is x + y/60
Hence angle of short hand = (x + y/60)*30
Hence angle of minute hand = 6*y
Since two hands are coincided
Hence (x + y/60)*30 = 6*y
Hence y = 30*x/(6 - 0.5)
Between 3 and 4 o'clock, x = 3
Hence y =90/5.5 = 16.3636 miniutes
Hence the angle is 98.1816 degrees
Verify
Angle of short hand = (3 + 16.3636/60)*30 = 98.18
Angle of long hand = 16.3636*6 = 98.18
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