Sol. 11 : 60 - 4 : 46 = 7 : 14
or
12 – 4 : 46 = 7 : 14
Sol. 23 : 60 - 12 : 35 = 11 : 25
Minute hand moves 30° in 5 minutes & 360° in 1 hour i.e. It moves 6° in One Minute Hour hand moves 30° in 60 minutes
In One minute, hour hand moves 0.5°
Both types of angles are 360° in total. If one angle is known, other can be obtained by subtracting from 360 0 .
Minutes of the given time are multiplied by 5x 1/2 ...... a, Hour hand is multiplied by 30......b, then a - b is the angle required.
Q1. Between 2 o'clock to 10 o'clock, how many times the hands of a clock are at right angle?
(a) 14
(b) 12
(c) 16
d) 15
Sol. Between 2 and 4 o'clock; 8 and 10 o'clock, the hands are at right thrice in each case. Between 4 and s8 o'clock, the hands are at right angles. So total number of times the hands are at right angles = 3 + 3 + (2 x 4) = 14. (a)
Q2. Find the angle between the hour hand and the minute hand of a clock when the time is 2:25
Sol. At 2:25, the hands of a clock are shown in the diagram. At 2 o'clock, the hour hand is at 2. In nest 25 minutes hour hand has moved 25 × 1/2 i.e. 12 1/20. Angle between 2 and 5 is 900. Thus the required angle is 900 – 12 1/20 = 771/20
Q3. Between 1 o'clock and 2 o'clock, find the time when the minute hand and an hour hand coincide.
Sol. At 1 o'clock, the minute hand is 5 minutes behind the hour hand. The minute hand gains 5 minutes in 5 x 12/11 minutes i.e. in 5 x 55/11 minutes past 1 o’clock.
Q1. What is a mirror image of the clock of 10 hours 35 minutes?
Ans. It will be 3:25
Q2. What is the mirror image of time 12 : 40?
Ans. Given time in the clock in mirror = 12 : 40. Real time + Mirror time = 24 : 00.
Q3. What is a mirror image of a 12 o' clock?
Ans. For every mirror image based on a clock, If it is a 12 hours clock, then subtract the given time from 11:60 hrs. And if it is a 24 hr clock, remove the given time from 23:60 hrs. Hence, the mirror image time will be 7'O clock.
Q4. What is the mirror image of the time is 7 : 35?
Ans. The attached image of the 7:35 time will look like and what time it will show. It will show the time of 4:25. The rule involved in this question is, The concept of reflection and how the distance factor affects the image formed in a plane mirror.
Q5. What is the mirror image of 12 :35?
Ans. 23: 60 - 12: 35 = 11: 25
A plane mirror is kept on the right of the clock, with its plane perpendicular to the face of the watch.
Q6. What will be the mirror image of 10 : 30?
Ans. 2:30 will be the mirror image of the clock showing the time 10:30.
Q7. What shows the time at 3 : 25 when seen through a mirror the time will appear to be?
Ans. A watch shows the time as 3: 25. When seen through a mirror, time will be Ignore the labels on the clock. A watch shows the time as 3: 25.