Clocks

Key Points

The face or dial of a watch is a circle whose circumference is divided into 60 equal part called minute spaces. A clock has two hands - the smaller one is called the hour hand or short hand while the larger one is called the minute hand or long hand.

1. In every 60 minutes, the minute hand gains 55 minutes on the hour hand.
2. In every hour, both the hands coincide once, i.e 0 degrees.
3. The hands are in the same straight line when they are coincident or opposite to each other. i.e 0 degrees or 180 degrees.
4. When the two hands are at right angles, they are 15 minute spaces apart, i.e 90 degrees.
5. When the hands are in the opposite directions, they are 30 minute spaces apart, i.e 180 degrees.
6. Angle traced by hour hand in 12 hrs = 360 degrees
7. Angle traced by minute hand in 60 min = 360 degrees
8. If a watch or a clock indicated 8.15, when the correct time is 8, it is said to be 15 minutes too fast. On the other hand if it indicates 7.45, when the correct time is 8, it is said to be 15 minutes slow.
9. 60 min is 360 degrees, so 1 min is 60 degrees.
10. The hands of a clock coincide in a day or 24 hours is 22 times, in 12 hours 11 minutes.
11. The hands of clock are straight in a day is 44 times.
12. The hands of a clock at right angle in a day is 44 times.
13. The hands of a clock in straight line but opposite in direction is 22 times per day,
14. Angle between the Hour hand and Minute hand is given by : |(11*m/2)-(30h)|