Clock - General Questions (2)

In 12 hours, they are at right angles 22 times.

 In 24 hours, they are at right angles 44 times.

Angle traced by hour hand in 12 hrs. = 360°.

Angle traced by it in	11	hrs =		360	x	11		°	= 110°.
	3			12		3

Angle traced by minute hand in 60 min. = 360°.

Angle traced by it in 40 min. =		360	x 40		°	= 240°.
		60

 Required angle (240 - 110)° = 130°.

Angle traced by hour hand in	13	hrs =		360	x	13		°	= 130°.
	3			12		3

Angle traced by min. hand in 20 min. =		360	x 20		°	= 120°.
		60

 Required angle = (130 - 120)° = 10°.

At 5 o'clock, the hands are 25 min. spaces apart.

To be at right angles and that too between 5.30 and 6, the minute hand has to gain (25 + 15) = 40 min. spaces.

55 min. spaces are gained in 60 min.

40 min. spaces are gained in		60	x 40	min	=	43	7	min.
		55					11

Required time = 43	7	min. past 5.
	11

When the hands of the clock are in the same straight line but not together, they are 30 minute spaces apart.

At 7 o'clock, they are 25 min. spaces apart.

 Minute hand will have to gain only 5 min. spaces.

55 min. spaces are gained in 60 min.

5 min. spaces are gained in		60	x 5	min	= 5	5	min.
		55				11

Required time = 5	5	min. past 7.
	11

55 min. spaces are covered in 60 min.

60 min. spaces are covered in		60	x 60	min.	= 65	5	min.
		55				11

Loss in 64 min. =		65	5	- 64		=	16	min.
			11				11

Loss in 24 hrs =		16	x	1	x 24 x 60	min.	=	32	8	min.
		11		64					11

3 min. 5 sec. of this clock = 3 min. of the correct clock.

	37	hrs of this clock =	1	hrs of the correct clock.
	720		20

	37	hrs of this clock =		1	x	720	x	37		hrs of the correct clock.
	4			20		37		4

      = 9 hrs of the correct clock.

 The correct time is 9 hrs after 7 a.m. i.e., 4 p.m.